QTI PDC interrupt controller

PDC is QTI's platform parent interrupt controller that serves as wakeup source.

Newer QTI SOCs are replacing MPM (MSM sleep Power Manager) with PDC (Power
Domain Controller) to manage subsystem wakeups and resources during sleep.
This driver marks the wakeup interrupts in APSS PDC such that it monitors the
interrupts when the system is asleep, wakes up the APSS when one of these
interrupts occur and replays it to the subsystem interrupt controller after it
becomes operational.

Earlier MPM architecture used arch-extension of GIC interrupt
controller to mark enabled wake-up interrupts and monitor these when the
system goes to sleep. Since the arch-extensions are no-longer available
on newer kernel versions, this driver is implemented as hierarchical irq
domain.  GIC is parent interrupt controller at the highest level.
Platform interrupt controller PDC is next in hierarchy, followed by others.
This driver only configures the interrupts, does not handle them.

PDC interrupt configuration involves programming of 2 set of registers:
IRQ_ENABLE_BANK    - Enable the irq
IRQ_i_CFG          - Configure the interrupt i

Properties:

- compatible:
	Usage: required
	Value type: <string>
	Definition: Should contain one of -
		    "qcom,pdc-sdm845",
		    "qcom,pdc-sdmmagpie",
		    "qcom,pdc-sm6150",
	            "qcom,pdc-sm8150",
		    "qcom,pdc-sdxprairie",
	            "qcom,pdc-atoll"

- reg:
	Usage: required
	Value type: <prop-encoded-array>
	Definition: Specifies the base physical address for PDC hardware
			block for DRV2.

- interrupt-cells:
	Usage: required
	Value type: <u32>
	Definition: Specifies the number of cells needed to encode an interrupt source.
			Value must be 3.
			The encoding of these cells are same as described in
			Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt

- interrupt-parent:
	Usage: required
	Value type: <phandle>
	Definition: Specifies the interrupt parent necessary for hierarchical domain to operate.

- interrupt-controller:
	Usage: required
	Value type: <bool>
	Definition: Identifies the node as an interrupt controller.

Example:

pdcgic: interrupt-controller@0xb220000{
	compatible = "qcom,pdc-sdm845";
	reg = <0xb220000 0x30000>;
	#interrupt-cells = <3>;
	interrupt-parent = <&intc>;
	interrupt-controller;
};
