Update specification for transfer list with GPT info tag

Add a new entry in the transfer list, to log the corruption
of primagry GPT (GUID partition table) header. This information can
indicate if the system is running under compromised condition
as it use backup GPT. The new entry is a information from
previous boot loading stage and thus follow the same category
as TL_TAG_EXEC_EP_INFO32

Signed-off-by: Xialin Liu <xialin.liu@arm.com>

Author: xialin-arm

source/transfer_list.rst

@@ -879,6 +879,9 @@ including TF-A, OP-TEE and Hafnium.
    * - :ref:`0x108 <tab_entry_point_info32>`
      - AArch32 Entry Point Info
 
+   * - :ref:`0x109 <tab_gpt_info>`
+     - GPT Error Info
+
 **OP-TEE pageable part address entry layout (XFERLIST_OPTEE_PAGEABLE_PART_ADDR)**
 
 This entry type holds the address of OP-TEE pageable part which is described in
@@ -1374,5 +1377,43 @@ subsequent images. It's usage is identical to the 64-bit form represented by
      - hdr_size + 0x20
      - Register R3.
 
+**GUID Partition Table (GPT) error information (XFERLIST_GPT_ERROR_INFO)**
+
+This entry holds an indication of the type of GPT error.
+`gpt_error_info` contains all possible GPT error information.
+It is an 8-bit value. Bit 0 indicates that the secondary GPT is being used,
+due to the corruption of the primary GPT header.
+Bits [7:1] are reserved for future use.
+
+.. _tab_gpt_info:
+.. list-table:: GPT info type layout
+   :widths: 2 2 2 8
+   :header-rows: 1
+
+   * - Field
+     - Size (bytes)
+     - Offset (bytes)
+     - Description
+
+   * - tag_id
+     - 0x3
+     - 0x0
+     - The tag_id field must be set to `0x109`.
+
+   * - hdr_size
+     - 0x1
+     - 0x3
+     - |hdr_size_desc|
+
+   * - data_size
+     - 0x1
+     - 0x4
+     - The size of the GPT error information in bytes, it is always 1 byte.
+
+   * - gpt_error_info
+     - data_size
+     - hdr_size
+     - The `gpt_error_info` field contains GPT error information.
+
 .. |hdr_size_desc| replace:: The size of this entry header in bytes must be set to `8`.
 .. |current_version| replace:: `0x1`