* Freescale Layerscape external IRQs

Some Layerscape SOCs (LS1021A, LS1043A, LS1046A) support inverting
the polarity of certain external interrupt lines.

The device node must be a child of the node representing the
Supplemental Configuration Unit (SCFG).

Required properties:
- compatible: should be "fsl,<soc-name>-extirq", e.g. "fsl,ls1021a-extirq".
- #interrupt-cells: Must be 2. The first element is the index of the
  external interrupt line. The second element is the trigger type.
- #address-cells: Must be 0.
- interrupt-controller: Identifies the node as an interrupt controller
- reg: Specifies the Interrupt Polarity Control Register (INTPCR) in
  the SCFG.
- interrupt-map: Specifies the mapping from external interrupts to GIC
  interrupts.
- interrupt-map-mask: Must be <0xffffffff 0>.

Example:
	scfg: scfg@1570000 {
		compatible = "fsl,ls1021a-scfg", "syscon";
		reg = <0x0 0x1570000 0x0 0x10000>;
		big-endian;
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0x0 0x0 0x1570000 0x10000>;

		extirq: interrupt-controller@1ac {
			compatible = "fsl,ls1021a-extirq";
			#interrupt-cells = <2>;
			#address-cells = <0>;
			interrupt-controller;
			reg = <0x1ac 4>;
			interrupt-map =
				<0 0 &gic GIC_SPI 163 IRQ_TYPE_LEVEL_HIGH>,
				<1 0 &gic GIC_SPI 164 IRQ_TYPE_LEVEL_HIGH>,
				<2 0 &gic GIC_SPI 165 IRQ_TYPE_LEVEL_HIGH>,
				<3 0 &gic GIC_SPI 167 IRQ_TYPE_LEVEL_HIGH>,
				<4 0 &gic GIC_SPI 168 IRQ_TYPE_LEVEL_HIGH>,
				<5 0 &gic GIC_SPI 169 IRQ_TYPE_LEVEL_HIGH>;
			interrupt-map-mask = <0xffffffff 0x0>;
		};
	};


	interrupts-extended = <&gic GIC_SPI 88 IRQ_TYPE_LEVEL_HIGH>,
			      <&extirq 1 IRQ_TYPE_LEVEL_LOW>;