mailbox: Add generic mechanism for testing Mailbox Controllers

This particular Client implementation uses shared memory in order
to pass messages between Mailbox users; however, it can be easily
hacked to support any type of Controller.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 7b53386..546d05f 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -78,4 +78,11 @@
 	  Mailbox implementation for STMicroelectonics family chips with
 	  hardware for interprocessor communication.
 
+config MAILBOX_TEST
+	tristate "Mailbox Test Client"
+	depends on OF
+	help
+	  Test client to help with testing new Controller driver
+	  implementations.
+
 endif