Samsung S3C24XX Interrupt Controllers

The S3C24XX SoCs contain a custom set of interrupt controllers providing a
varying number of interrupt sources. The set consists of a main- and sub-
controller and on newer SoCs even a second main controller.

Required properties:
- compatible: Compatible property value should be "samsung,s3c2410-irq"
  for machines before s3c2416 and "samsung,s3c2416-irq" for s3c2416 and later.

- reg: Physical base address of the controller and length of memory mapped
  region.

- interrupt-controller : Identifies the node as an interrupt controller

- #interrupt-cells : Specifies the number of cells needed to encode an
  interrupt source. The value shall be 4 and interrupt descriptor shall
  have the following format:
      <ctrl_num parent_irq ctrl_irq type>

  ctrl_num contains the controller to use:
      - 0 ... main controller
      - 1 ... sub controller
      - 2 ... second main controller on s3c2416 and s3c2450
  parent_irq contains the parent bit in the main controller and will be
             ignored in main controllers
  ctrl_irq contains the interrupt bit of the controller
  type contains the trigger type to use

Example:

	interrupt-controller@4a000000 {
		compatible = "samsung,s3c2410-irq";
		reg = <0x4a000000 0x100>;
		interrupt-controller;
		#interrupt-cells=<4>;
	};

	[...]

	serial@50000000 {
		compatible = "samsung,s3c2410-uart";
		reg = <0x50000000 0x4000>;
		interrupt-parent = <&subintc>;
		interrupts = <1 28 0 4>, <1 28 1 4>;
	};

	rtc@57000000 {
		compatible = "samsung,s3c2410-rtc";
		reg = <0x57000000 0x100>;
		interrupt-parent = <&intc>;
		interrupts = <0 30 0 3>, <0 8 0 3>;
	};