dt-bindings: net: dsa: add MT7530 interrupt controller binding

Add device tree binding to support MT7530 interrupt controller.
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/mt7530.txt

@@ -81,6 +81,12 @@ Optional properties:
 - gpio-controller: Boolean; if defined, MT7530's LED controller will run on
 	GPIO mode.
 - #gpio-cells: Must be 2 if gpio-controller is defined.
+- interrupt-controller: Boolean; Enables the internal interrupt controller.
+
+If interrupt-controller is defined, the following properties are required.
+
+- #interrupt-cells: Must be 1.
+- interrupts: Parent interrupt for the interrupt controller.
 
 See Documentation/devicetree/bindings/net/dsa/dsa.txt for a list of additional
 required, optional properties and how the integrated switch subnodes must