* Synopsys DesignWare APB GPIO controller

Required properties:
- compatible : Should be "snps,dw-apb-gpio"
- reg : Address and length of the register set for the device

The GPIO controller has a configurable number of banks, each of which are
represented as child nodes with the following properties:

Required properties:
- compatible : "snps,dw-apb-gpio-bank"
- gpio-controller : Marks the device node as a gpio controller.
- #gpio-cells : Should be two.  The first cell is the pin number and
  the second cell is used to specify optional parameters (currently
  unused).
- reg : The integer bank index of the bank, a single cell.
- nr-gpio : The number of pins in the bank, a single cell.

Optional properties:
- interrupt-controller : The first bank may be configured to be an interrupt
controller.
- #interrupt-cells : Specifies the number of cells needed to encode an
interrupt.  Shall be set to 2.  The first cell defines the interrupt number,
the second encodes the triger flags encoded as described in
Documentation/devicetree/bindings/interrupts.txt
- interrupt-parent : The parent interrupt controller.
- interrupts : The interrupts to the parent controller raised when GPIOs
generate the interrupts.

Example:

gpio: gpio@20000 {
	compatible = "snps,dw-apb-gpio";
	reg = <0x20000 0x1000>;
	#address-cells = <1>;
	#size-cells = <0>;

	banka: gpio-controller@0 {
		compatible = "snps,dw-apb-gpio-bank";
		gpio-controller;
		#gpio-cells = <2>;
		nr-gpio = <8>;
		reg = <0>;
		interrupt-controller;
		#interrupt-cells = <2>;
		interrupt-parent = <&vic1>;
		interrupts = <0 1 2 3 4 5 6 7>;
	};

	bankb: gpio-controller@1 {
		compatible = "snps,dw-apb-gpio-bank";
		gpio-controller;
		#gpio-cells = <2>;
		nr-gpio = <8>;
		reg = <1>;
	};
};