diff --git a/CMakeLists.txt b/CMakeLists.txt
index 92ef83a..32cfd14 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -134,6 +134,7 @@
             "${AOM_ROOT}/aom/aom_codec.h"
             "${AOM_ROOT}/aom/aom_decoder.h"
             "${AOM_ROOT}/aom/aom_encoder.h"
+            "${AOM_ROOT}/aom/aom_external_partition.h"
             "${AOM_ROOT}/aom/aom_frame_buffer.h"
             "${AOM_ROOT}/aom/aom_image.h"
             "${AOM_ROOT}/aom/aom_integer.h"
diff --git a/aom/aom_encoder.h b/aom/aom_encoder.h
index b2926e1..b0784a0 100644
--- a/aom/aom_encoder.h
+++ b/aom/aom_encoder.h
@@ -31,6 +31,7 @@
 #endif
 
 #include "aom/aom_codec.h"
+#include "aom/aom_external_partition.h"
 
 /*!\brief Current ABI version number
  *
@@ -41,7 +42,7 @@
  * fields to structures
  */
 #define AOM_ENCODER_ABI_VERSION \
-  (9 + AOM_CODEC_ABI_VERSION) /**<\hideinitializer*/
+  (9 + AOM_CODEC_ABI_VERSION + AOM_EXT_PART_ABI_VERSION) /**<\hideinitializer*/
 
 /*! \brief Encoder capabilities bitfield
  *
diff --git a/aom/aom_external_partition.h b/aom/aom_external_partition.h
new file mode 100644
index 0000000..129ef3a
--- /dev/null
+++ b/aom/aom_external_partition.h
@@ -0,0 +1,202 @@
+/*
+ * Copyright (c) 2021, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+#ifndef AOM_AOM_AOM_EXTERNAL_PARTITION_H_
+#define AOM_AOM_AOM_EXTERNAL_PARTITION_H_
+
+/*!\defgroup aom_encoder AOMedia AOM/AV1 Encoder
+ * \ingroup aom
+ *
+ * @{
+ */
+#include "./aom_integer.h"
+
+/*!\file
+ * \brief Provides function pointer definitions for the external partition.
+ */
+
+/*!\brief Current ABI version number
+ *
+ * \internal
+ * If this file is altered in any way that changes the ABI, this value
+ * must be bumped. Examples include, but are not limited to, changing
+ * types, removing or reassigning enums, adding/removing/rearranging
+ * fields to structures.
+ */
+#define AOM_EXT_PART_ABI_VERSION (1)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*!\brief Abstract external partition model handler
+ */
+typedef void *aom_ext_part_model_t;
+
+/*!\brief Config information sent to the external partition model.
+ *
+ * For example, the maximum superblock size determined by the sequence header.
+ */
+typedef struct aom_ext_part_config {
+  int superblock_size; /**< super block size (either 64x64 or 128x128) */
+} aom_ext_part_config_t;
+
+/*!\brief Features pass to the external model to make partition decisions.
+ *
+ * The encoder sends these features to the external model through
+ * "func()" defined in .....
+ *
+ * NOTE: new member variables may be added to this structure in the future.
+ * Once new features are finalized, bump the major version of libaom.
+ */
+typedef struct aom_partition_features {
+  // Features are unclear yet
+  // Candidates include:
+  // mv
+  int64_t sse; /**< sum squared error */
+} aom_partition_features_t;
+
+/*!\brief Partition decisions received from the external model.
+ *
+ * The encoder receives partition decisions and encodes the superblock
+ * with the given partition type.
+ * The encoder receives it from "func()" define in ....
+ *
+ * NOTE: new member variables may be added to this structure in the future.
+ * Once new features are finalized, bump the major version of libaom.
+ */
+typedef struct aom_partition_decision {
+  int is_final_decision;       /**< The flag whether it is the final decision */
+  int partition_decision[256]; /**< Partition decisions */
+} aom_partition_decision_t;
+
+/*!\brief Encoding stats for the given partition decision.
+ *
+ * The encoding stats collected by encoding the superblock with the
+ * given partition types.
+ * The encoder sends the stats to the external model for training
+ * or inference though "func()" defined in ....
+ */
+typedef struct aom_partition_stats {
+  int rate;       /**< Rate cost of the block */
+  int64_t dist;   /**< Distortion of the block */
+  int64_t rdcost; /**< Rate-distortion cost of the block */
+} aom_partition_stats_t;
+
+/*!\brief Enum for return status.
+ */
+typedef enum aom_ext_part_status {
+  AOM_EXT_PART_OK = 0,    /**< Status of success */
+  AOM_EXT_PART_ERROR = 1, /**< Status of failure */
+} aom_ext_part_status_t;
+
+/*!\brief Callback of creating an external partition model.
+ *
+ * The callback is invoked by the encoder to create an external partition
+ * model.
+ *
+ * \param[in] priv Callback's private data
+ * \param[in] part_config Config information pointer for model creation
+ * \param[out] ext_part_model Pointer to the model
+ */
+typedef aom_ext_part_status_t (*aom_ext_part_create_model_fn_t)(
+    void *priv, const aom_ext_part_config_t *part_config,
+    aom_ext_part_model_t *ext_part_model);
+
+/*!\brief Callback of sending features to the external partition model.
+ *
+ * The callback is invoked by the encoder to send features to the external
+ * partition model.
+ *
+ * \param[in] ext_part_model The external model
+ * \param[in] part_features Pointer to the features
+ */
+typedef aom_ext_part_status_t (*aom_ext_part_send_features_fn_t)(
+    aom_ext_part_model_t ext_part_model,
+    const aom_partition_features_t *part_features);
+
+/*!\brief Callback of receiving partition decisions from the external
+ * partition model.
+ *
+ * The callback is invoked by the encoder to receive partition decisions from
+ * the external partition model.
+ *
+ * \param[in] ext_part_model The external model
+ * \param[in] ext_part_decision Pointer to the partition decisions
+ */
+typedef aom_ext_part_status_t (*aom_ext_part_get_decision_fn_t)(
+    aom_ext_part_model_t ext_part_model,
+    aom_partition_decision_t *ext_part_decision);
+
+/*!\brief Callback of sending stats to the external partition model.
+ *
+ * The callback is invoked by the encoder to send encoding stats to
+ * the external partition model.
+ *
+ * \param[in] ext_part_model The external model
+ * \param[in] ext_part_stats Pointer to the encoding stats
+ */
+typedef aom_ext_part_status_t (*aom_ext_part_send_partition_stats_fn_t)(
+    aom_ext_part_model_t ext_part_model,
+    const aom_partition_stats_t *ext_part_stats);
+
+/*!\brief Callback of deleting the external partition model.
+ *
+ * The callback is invoked by the encoder to delete the external partition
+ * model.
+ *
+ * \param[in] ext_part_model The external model
+ */
+typedef aom_ext_part_status_t (*aom_ext_part_delete_model_fn_t)(
+    aom_ext_part_model_t ext_part_model);
+
+/*!\brief Callback function set for external partition model.
+ *
+ * Uses can enable external partition model by registering a set of
+ * callback functions with the flag: AV1E_SET_EXTERNAL_PARTITION_MODEL
+ */
+typedef struct aom_ext_part_funcs {
+  /*!
+   * Create an external partition model.
+   */
+  aom_ext_part_create_model_fn_t create_model;
+
+  /*!
+   * Send features to the external partition model to make partition decisions.
+   */
+  aom_ext_part_send_features_fn_t send_features;
+
+  /*!
+   * Get partition decisions from the external partition model.
+   */
+  aom_ext_part_get_decision_fn_t get_partition_decision;
+
+  /*!
+   * Send stats of the current partition to the external model.
+   */
+  aom_ext_part_send_partition_stats_fn_t send_partition_stats;
+
+  /*!
+   * Delete the external partition model.
+   */
+  aom_ext_part_delete_model_fn_t delete_model;
+
+  /*!
+   * Private data for the external partition model.
+   */
+  void *priv;
+} aom_ext_part_funcs_t;
+
+/*!@} - end defgroup aom_encoder*/
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // AOM_AOM_AOM_EXTERNAL_PARTITION_H_
diff --git a/build/cmake/aom_install.cmake b/build/cmake/aom_install.cmake
index 2c0e7a5..ebdbe91 100644
--- a/build/cmake/aom_install.cmake
+++ b/build/cmake/aom_install.cmake
@@ -19,7 +19,8 @@
 
 if(CONFIG_AV1_ENCODER)
   list(APPEND AOM_INSTALL_INCS "${AOM_ROOT}/aom/aomcx.h"
-              "${AOM_ROOT}/aom/aom_encoder.h")
+              "${AOM_ROOT}/aom/aom_encoder.h"
+              "${AOM_ROOT}/aom/aom_external_partition.h")
 endif()
 
 # Generate aom.pc and setup dependencies to ensure it is created when necessary.
diff --git a/docs.cmake b/docs.cmake
index 7973524..b2d3083 100644
--- a/docs.cmake
+++ b/docs.cmake
@@ -25,6 +25,7 @@
     "${AOM_ROOT}/aom/aom_codec.h"
     "${AOM_ROOT}/aom/aom_decoder.h"
     "${AOM_ROOT}/aom/aom_encoder.h"
+    "${AOM_ROOT}/aom/aom_external_partition.h"
     "${AOM_ROOT}/aom/aom_frame_buffer.h"
     "${AOM_ROOT}/aom/aom_image.h"
     "${AOM_ROOT}/aom/aom_integer.h"