feat(smcc): introduce a new vendor_el3 service for ACS SMC handler

In preparation to add support for the Architecture Compliance Suite
SMC services, reserve a SMC ID and introduce a handler function.
Currently, an empty placeholder function is added and future support
will be introduced for the handler support.

More info on System ACS, please refer below link,
https://developer.arm.com/Architectures/Architectural%20Compliance%20Suite

Signed-off-by: Nandan J <Nandan.J@arm.com>
Change-Id: Ib13ccae9d3829e3dcd1cd33c4a7f27efe1436d03
diff --git a/docs/components/ven-el3-service.rst b/docs/components/ven-el3-service.rst
index 13449ba..8be1b39 100644
--- a/docs/components/ven-el3-service.rst
+++ b/docs/components/ven-el3-service.rst
@@ -32,9 +32,13 @@
 +-----------------------------------+ Measurement Framework | | 2 - 15 are reserved for future expansion. |
 | 0xC7000020 - 0xC700002F (SMC64)   | (PMF)                 |                                             |
 +-----------------------------------+-----------------------+---------------------------------------------+
-| 0x87000030 - 0x8700FFFF (SMC32)   | Reserved              | | reserved for future expansion             |
+| 0x87000030 - 0x8700003F (SMC32)   | ACS (Architecture     | | 0 in use.                                 |
++-----------------------------------+ Compliance Suite) SMC | | 1 - 15 are reserved for future expansion. |
+| 0xC7000030 - 0xC700003F (SMC64)   | handler               |                                             |
++-----------------------------------+-----------------------+---------------------------------------------+
+| 0x87000040 - 0x8700FFFF (SMC32)   | Reserved              | | reserved for future expansion             |
 +-----------------------------------+                       |                                             |
-| 0xC7000030 - 0xC700FFFF (SMC64)   |                       |                                             |
+| 0xC7000040 - 0xC700FFFF (SMC64)   |                       |                                             |
 +-----------------------------------+-----------------------+---------------------------------------------+
 
 Source definitions for vendor-specific EL3 Monitor Service Calls used by TF-A are located in
@@ -45,6 +49,8 @@
 +============================+============================+================================+
 |                          1 |                          0 | Added Debugfs and PMF services.|
 +----------------------------+----------------------------+--------------------------------+
+|                          1 |                          1 | Added ACS SMC handler services.|
++----------------------------+----------------------------+--------------------------------+
 
 *Table 1: Showing different versions of Vendor-specific service and changes done with each version*
 
@@ -71,8 +77,16 @@
 The optional DebugFS interface is accessed through Vendor specific EL3 service. Refer
 to :ref:`DebugFS interface` documentation for further details and usage.
 
+Architecture Compliance Suite (ACS) SMC handler
+-----------------------------------------------
+
+The Architecture Compliance Suite (ACS) SMC handler allows callers to branch
+to their ACS EL3 code based on their respective use-cases.
+For more details on System ACS, `System ACS`_.
+
 --------------
 
-*Copyright (c) 2024, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2024-2025, Arm Limited and Contributors. All rights reserved.*
 
+.. _System ACS: https://developer.arm.com/Architectures/Architectural%20Compliance%20Suite
 .. _SMC Calling Convention: https://developer.arm.com/docs/den0028/latest
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 32daf1e..1b3568e 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -1509,6 +1509,11 @@
    information using HOB defined in `Platform Initialization specification`_.
    This defaults to ``0``.
 
+-  ``ENABLE_ACS_SMC``: When set to ``1``, this enables support for ACS SMC
+   handler code to handle SMC calls from the Architecture Compliance Suite. The
+   handler is intentionally empty to reserve the SMC section and allow
+   project-specific implementations in future ACS use cases.
+
 Firmware update options
 ~~~~~~~~~~~~~~~~~~~~~~~