Add platform certification documentation

Adds documents about the TS project relationship with PSA Certified
and SystemReady certification programmes.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I7e8294bd3a9a2c8c2b4bad2e2ca8b2f26cb157b7
diff --git a/docs/certification/system-ready.rst b/docs/certification/system-ready.rst
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+SystemReady
+===========
+Arm SystemReady is a compliance certification programme that aims to promote a standardized
+view of a platform and its firmware (see: `Arm SystemReady`_). SystemReady may be applied across
+different classes of device, represented by different SystemReady bands, from resource constrained
+IoT devices through to servers. By standardizing the platform and its firmware, generic operating
+systems can be expected to 'just work' on any compliant device.
+
+SystemReady leverages existing open standards such as UEFI. The Trusted Services project
+includes service level components that enable UEFI SMM services to be realized, backed by PSA
+root-of-trust services. As an alternative to EDK2 StMM, the smm-gateway deployment presents
+UEFI compliant SMM service endpoints, backed by the generic Secure Storage and Crypto services.
+For more information, see:
+
+    * :ref:`Secure Partition Images`
+    * :ref:`UEFI SMM Services`
+
+The UEFI features supported by smm-gateway are designed to meet SystemReady requirements for
+the IR band (embedded IoT).
+
+--------------
+
+.. _`Arm SystemReady`: https://developer.arm.com/architectures/system-architectures/arm-systemready
+
+*Copyright (c) 2022, Arm Limited and Contributors. All rights reserved.*
+
+SPDX-License-Identifier: BSD-3-Clause