OpenRISC 1000 Programmable Interrupt Controller

Required properties:

- compatible : should be "opencores,or1k-pic-level" for variants with
  level triggered interrupt lines, "opencores,or1k-pic-edge" for variants with
  edge triggered interrupt lines or "opencores,or1200-pic" for machines
  with the non-spec compliant or1200 type implementation.

  "opencores,or1k-pic" is also provided as an alias to "opencores,or1200-pic",
  but this is only for backwards compatibility.

- 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 1.

Example:

intc: interrupt-controller {
	compatible = "opencores,or1k-pic-level";
	interrupt-controller;
	#interrupt-cells = <1>;
};
