doc: Add a binding document for COT descriptors

Added a binding document for COT descriptors which is going
to be used in order to create COT desciptors at run-time.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: Ic54519b0e16d145cd1609274a00b137a9194e8dd
diff --git a/docs/components/index.rst b/docs/components/index.rst
index c5f6264..18b1e38 100644
--- a/docs/components/index.rst
+++ b/docs/components/index.rst
@@ -19,3 +19,4 @@
    secure-partition-manager-design
    psa-ffa-manifest-binding
    xlat-tables-lib-v2-design
+   cot-binding