use static admin key from cluster model if manage_admin_key is set to True

Change-Id: I6aef0ca8faf6f9443b505895e5b226e8376e573a
Related-Prod: PROD-32112
diff --git a/README.rst b/README.rst
index a0c3d3c..9d1b8a4 100644
--- a/README.rst
+++ b/README.rst
@@ -525,10 +525,11 @@
             ...
 
 
-Ceph manage keyring keys
+Ceph manage clients keyring keys
 ------------------------
 
-Keyrings are dynamically generated unless specified by the following pillar.
+Keyrings are dynamically generated unless specified by the manage_keyring pillar.
+This settings has no effect on admin keyring.
 
 .. code-block:: yaml
 
@@ -543,6 +544,21 @@
               mon: "allow r"
               osd: "allow class-read object_prefix rdb_children, allow rwx pool=images"
 
+Ceph manage admin keyring
+--------------------------
+To use pre-defined admin key add manage_admin_keyring and admin keyring definition to ceph mon nodes in cluster_model/ceph/mon.yml
+
+ceph:
+  common:
+    manage_admin_keyring: true
+    keyring:
+      admin:
+        caps:
+          mds: "allow *"
+          mgr: "allow *"
+          mon: "allow *"
+          osd: "allow *"
+        key: AACf3ulZFFPNDxAAd2DWds3aEkHh4IklZVgIaQ==
 
 Generate CRUSH map - Recommended way
 -----------------------------------