Docs: Platform documentation rules

- Minimal rules for a platform documentation
- Adjust existing platforms according to the rules

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: Idcb85f8ed5d55aa6406cd48cdfcb558d92ff0647
diff --git a/docs/platform/arm/index.rst b/docs/platform/arm/index.rst
index 68eb5c5..4bb36c4 100755
--- a/docs/platform/arm/index.rst
+++ b/docs/platform/arm/index.rst
@@ -3,7 +3,7 @@
 #############
 
 .. toctree::
-    :maxdepth: 2
+    :maxdepth: 1
     :titlesonly:
 
     Corstone-1000 <corstone1000/readme.rst>