diff --git a/docs/developer/service-descriptions/uml/SmmGatewayOverview.puml b/docs/developer/service-descriptions/uml/SmmGatewayOverview.puml
new file mode 100644
index 0000000..f53d2a4
--- /dev/null
+++ b/docs/developer/service-descriptions/uml/SmmGatewayOverview.puml
@@ -0,0 +1,14 @@
+'-------------------------------------------------------------------------------
+' Copyright (c) 2021-2022, Arm Limited and Contributors. All rights reserved.
+'
+' SPDX-License-Identifier: BSD-3-Clause
+'
+'-------------------------------------------------------------------------------
+
+@startuml
+
+[u-boot efi services] -down- [smm gateway]
+[smm gateway] -down- [secure storage service]
+[smm gateway] -down- [crypto service]
+
+@enduml