Add cross-reference to PQC Extension from Crypto spec.

Author: athoelke

doc/crypto/overview/intro.rst

@@ -26,6 +26,12 @@ This document includes:
 *   General considerations for implementers of this specification, and for applications that use the interface defined in this specification. See :secref:`implementation-considerations` and :secref:`usage-considerations`.
 *   A detailed definition of the API. See :secref:`library-management`, :secref:`key-management`, and :secref:`crypto-operations`.
 
+:cite-title:`PSA-PQC` is a companion document for version 1.3 of this specification.
+`[PSA-PQC]` defines an API for :term:`Post-Quantum Cryptography` (PQC) algorithms.
+The PQC API is a proposal at BETA status.
+The API defined by `[PSA-PQC]` is provided in a separate specification to reflect the different status of this API, and indicate that a future version can include incompatible changes to the PQC API.
+When the PQC API is stable, it will be included in a future version of the |API| specification.
+
 In future, companion documents will define *profiles* for this specification. A profile is
 a minimum mandatory subset of the interface that a compliant implementation must
 provide.

doc/crypto/references

@@ -396,3 +396,8 @@
     :author: Thread Group
     :publication: July 2022
     :url: www.threadgroup.org/ThreadSpec
+
+.. reference:: PSA-PQC
+    :title: PSA Certified Crypto API 1.3 PQC Extension
+    :doc_no: ARM AES 0119
+    :url: arm-software.github.io/psa-api/crypto

doc/crypto/terms

@@ -186,3 +186,8 @@
     application instances.
 
     See :secref:`isolation`.
+
+.. term:: Post-Quantum Cryptography
+    :abbr: PQC
+
+    A cryptographic scheme that relies on mathematical problems that do not have efficient algorithms for either classical or quantum computing.