Add sp environment documentation

Explain differences between opteesp and sp environments, along
documenting the build process of sp deployments.

Signed-off-by: Imre Kis <imre.kis@arm.com>
Change-Id: I036c30e730c355c134d3167f44723cd3a400bf77
diff --git a/docs/services/secure-storage-service-description.rst b/docs/services/secure-storage-service-description.rst
index 03295bf..f786af5 100644
--- a/docs/services/secure-storage-service-description.rst
+++ b/docs/services/secure-storage-service-description.rst
@@ -150,7 +150,7 @@
 ''''''''''''''''''''''''''''''''''''''''''''''''
 The Crypto service provider uses the Mbed Crypto portion of Mbed TLS to implement crypto
 operations.  Persistent keys are stored via the PSA Internal Trusted Storage C API.
-In the opteesp deployment of the Crypto service provider, a storage client backend is
+In the opteesp and sp deployments of the Crypto service provider, a storage client backend is
 used that accesses a secure store provided by a separate secure partition.  The following
 deployment diagram illustrates the storage frontend/backend combination used:
 
@@ -167,6 +167,6 @@
 
 --------------
 
-*Copyright (c) 2022, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2022-2023, Arm Limited and Contributors. All rights reserved.*
 
 SPDX-License-Identifier: BSD-3-Clause