ARM: bcm2835: Add the firmware driver information to the RPi DT

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

arch/arm/boot/dts/bcm2835-rpi.dtsi

@@ -14,6 +14,13 @@
 			linux,default-trigger = "heartbeat";
 		};
 	};
+
+	soc {
+		firmware: firmware {
+			compatible = "raspberrypi,bcm2835-firmware";
+			mboxes = <&mailbox>;
+		};
+	};
 };
 
 &gpio {