docs: add Measured Boot design

Added design document for Measured Boot implementation in
TF-A.

Change-Id: I25b57ec555b289eb6bbf0a6aae014d7bf6d152fd
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/docs/design_documents/measured_boot_poc.rst b/docs/design_documents/measured_boot_poc.rst
index 7f9519e..86cf4d1 100644
--- a/docs/design_documents/measured_boot_poc.rst
+++ b/docs/design_documents/measured_boot_poc.rst
@@ -10,6 +10,8 @@
 This section focuses on the `TCG event log`_ backend, which stores measurements
 in secure memory.
 
+See details of :ref:`Measured Boot Design`.
+
 The driver also provides mechanisms to pass the Event Log to normal world if
 needed.