Add 32-bit variant of XFERLIST_RW_MEM_LAYOUT

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>

source/transfer_list.rst

@@ -1006,6 +1006,8 @@ hand-over execution.
      - hdr_size
      - Holds the FF-A SP binary.
 
+.. _64_bit_mem_layout:
+
 **Read-Write Memory Layout Entry Layout (XFERLIST_RW_MEM_LAYOUT64)**
 
 This entry type holds a structure that describes the layout of a read-write
@@ -1171,6 +1173,47 @@ subsequent images. It's usage is identical to the 64-bit form represented by
      - hdr_size
      - Holds a single `entry_point_info` structure.
 
+**Read-Write Memory Layout Entry Layout (XFERLIST_RW_MEM_LAYOUT32)**
+
+This entry type holds the 32-bit variant of
+:ref:`XFERLIST_RW_MEM_LAYOUT64<64_bit_mem_layout>`. It is a structure used to
+describe the layout of a read-write memory region. TF-A utilizes this entry type
+to notify BL2 of the available memory for read-write operations. Note, for other
+memory types, such as read-only memory, distinct entries should be created.
+
+.. _tab_rw_mem_layout32:
+.. list-table:: Layout for a RW memory layout entry (32-bit variant)
+   :widths: 2 5 5 6
+
+   * - Field
+     - Size (bytes)
+     - Offset (bytes)
+     - Description
+
+   * - tag_id
+     - 0x3
+     - 0x0
+     - The tag_id field must be set to **0x107**.
+
+   * - hdr_size
+     - 0x1
+     - 0x3
+     - |hdr_size_desc|
+
+   * - data_size
+     - 0x4
+     - 0x4
+     - The size of the layout in bytes.
+
+   * - addr
+     - 0x4
+     - hdr_size
+     - The 32-bit base address of the memory region.
+
+   * - size
+     - 0x4
+     - hdr_size + 0x4
+     - The size of the memory region.
 
 .. |hdr_size_desc| replace:: The size of this entry header in bytes must be set to **8**.
 .. |current_version| replace:: `0x1`