diff --git a/docs/developer/uml/RpcSessionClassDiagram.puml b/docs/developer/uml/RpcSessionClassDiagram.puml
new file mode 100644
index 0000000..d264560
--- /dev/null
+++ b/docs/developer/uml/RpcSessionClassDiagram.puml
@@ -0,0 +1,20 @@
+'-------------------------------------------------------------------------------
+' Copyright (c) 2020-2021, Arm Limited and Contributors. All rights reserved.
+'
+' SPDX-License-Identifier: BSD-3-Clause
+'
+'-------------------------------------------------------------------------------
+
+@startuml
+
+class rpc_caller {
+	{abstract}int call(opcode, param_buf, result_buf)
+}
+
+rpc_caller -> call_ep
+note right on link
+Association with call_ep is made when
+RPC session is established.
+end note
+
+@enduml
\ No newline at end of file