Docs: Add documentation for RSS host communication

Signed-off-by: Jamie Fox <jamie.fox@arm.com>
Change-Id: Ib4447b894548c5483ef4ffa007e64d88cd9989ba
diff --git a/docs/platform/arm/index.rst b/docs/platform/arm/index.rst
index 46fe123..68eb5c5 100755
--- a/docs/platform/arm/index.rst
+++ b/docs/platform/arm/index.rst
@@ -3,7 +3,8 @@
 #############
 
 .. toctree::
-    :maxdepth: 1
+    :maxdepth: 2
+    :titlesonly:
 
     Corstone-1000 <corstone1000/readme.rst>
     Corstone-300 FPGA (AN547) <mps3/an547/README.rst>
@@ -11,7 +12,7 @@
     Corstone-310 FVP <mps3/corstone310/README.rst>
     Musca-B1 <musca_b1/readme.rst>
     Musca-S1 <musca_s1/readme.rst>
-    Runtime Security Subsystem <rss/readme.rst>
+    Runtime Security Subsystem <rss/index>
 
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