diff --git a/docs/environments/secure-partitions/index.rst b/docs/environments/secure-partitions/index.rst
index 9ab70d1..d57b103 100644
--- a/docs/environments/secure-partitions/index.rst
+++ b/docs/environments/secure-partitions/index.rst
@@ -1,16 +1,40 @@
 Secure Partitions
 =================
 
+:term:`Secure Partitions<Secure Partition>` are defined by the :term:`FF-A` standard
+
+Secure partitions are isolated processing environments managed by a Secure Partition Manager (SPM).
+An SPM performs the role of hypervisor for the Arm Secure state and is responsible for managing
+SP initialization, memory management and messaging. The Arm Firmware Framework for A-Profile (FF-A)
+specification (`FF-A Specification`_) defines the set of firmware features that enable the use of
+secure partitions for protecting sensitive workloads.
+
+The Armv8.4 architecture introduces the virtualization extension in the Secure state. For silicon
+based on Armv8.4 (or above) that implement the Secure-EL2 extension, the `Hafnium Project`_
+provides a reference SPM implementation. For pre-Arm8.4 silicon, the `OP-TEE Project`_ provides
+an alternative reference SPM implementation.
+
+Within the Trusted Services, the environments realized by the two reference SPM implementations
+are named as follows:
+
+    * *hfsp* - for service deployment under Hafnium
+    * *opteesp* - for service deployment under OP-TEE
+
 .. toctree::
     :maxdepth: 1
     :caption: Contents:
 
+    ff-a/index
+    spm/optee/index
+    spm/hafnium/index
     libsp
-    userspace-programs-on-fvp
-    opteesp-deployment-guide
 
 --------------
 
+.. _`FF-A Specification`: https://developer.arm.com/documentation/den0077/latest
+.. _`Hafnium Project`: https://www.trustedfirmware.org/projects/hafnium/
+.. _`OP-TEE Project`: https://www.trustedfirmware.org/projects/op-tee/
+
 *Copyright (c) 2020-2022, Arm Limited and Contributors. All rights reserved.*
 
 SPDX-License-Identifier: BSD-3-Clause