dt-bindings: Add root properties for Raspberry Pi 3

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/bcm/brcm,bcm2835.txt

@@ -30,6 +30,10 @@ Raspberry Pi 2 Model B
 Required root node properties:
 compatible = "raspberrypi,2-model-b", "brcm,bcm2836";
 
+Raspberry Pi 3 Model B
+Required root node properties:
+compatible = "raspberrypi,3-model-b", "brcm,bcm2837";
+
 Raspberry Pi Compute Module
 Required root node properties:
 compatible = "raspberrypi,compute-module", "brcm,bcm2835";