chapter3: add SCMI requirements

Add requirements on AArch64 platforms, when SCMI is implemented.
The requirements are on the minimum required and recommended versions for
the implemented SCMI protocols.
This corresponds to requiring at least SCMI 2.0 B, and ideally SCMI 3.2 E.

Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>

Author: vstehle

source/chapter3-secureworld.rst

@@ -73,6 +73,64 @@ defined in [PFDI]_ § 5 Compliance Requirements, and it must support a version
    request fault detection checks from Platform Firmware.
    At the time of writing, only PFDI version 1.0 is defined.
 
+AArch64 System Control and Management
+-------------------------------------
+
+On AArch64 platforms, when the System Control and Management Interface (SCMI) is
+described in the ACPI table or the Devicetree, it must conform to the Arm System
+Control and Management Interface specification [SCMI]_ and the following
+implementation requirements take precedence. [#SCMINote]_
+
+.. [#SCMINote] SCMI is a set of software interfaces defined by Arm, used for
+   system management.
+   It can be implemented by privileged or secure firmware, or by another
+   processor.
+
+.. list-table:: SCMI Implementation Requirements
+   :widths: 33 33 33
+   :header-rows: 1
+
+   * - SCMI Protocol
+     - Minimum required version (when implemented)
+     - Minimum recommended version (when implemented)
+   * - Base
+     - 2.0
+     - 2.1
+   * - Power domain management
+     - 2.0
+     - 3.1
+   * - System power management
+     -
+     - 2.1
+   * - Performance domain management
+     - 2.0
+     - 4.0
+   * - Clock management
+     -
+     - 3.0
+   * - Sensor management
+     -
+     - 3.1
+   * - Reset domain management
+     -
+     - 3.1
+   * - Voltage domain management
+     -
+     - 2.1
+   * - Power capping and monitoring
+     -
+     - 2.0
+   * - Pin control
+     -
+     -
+   * - System telemetry
+     -
+     -
+
+.. note:: SCMI specification v3.2 introduced version negotiation, which eases
+   agents and platforms interoperability, and this is therefore the recommended
+   implementation.
+
 RISC-V Multiprocessor Startup Protocol
 ======================================