STM32 External Interrupt Controller

Required properties:

- compatible: Should be:
    "st,stm32-exti"
    "st,stm32h7-exti"
    "st,stm32mp1-exti"
- reg: Specifies base physical address and size of the registers
- interrupt-controller: Indentifies the node as an interrupt controller
- #interrupt-cells: Specifies the number of cells to encode an interrupt
  specifier, shall be 2
- interrupts: interrupts references to primary interrupt controller
  (only needed for exti controller with multiple exti under
  same parent interrupt: st,stm32-exti and st,stm32h7-exti)

Optional properties:

- hwlocks: reference to a phandle of a hardware spinlock provider node.

Exti could have several parent interrupt controllers. In this case child nodes
are used to describe those "extra" parent controllers. Properties to use are:

- interrupt-controller: Indentifies the node as an interrupt controller
- #interrupt-cells: Specifies the number of cells to encode an interrupt
  specifier, shall be 2
- interrupt-parent: Phandle to the interrupt parent node.
- st,irq-number: Interrupt number mapped on the parent.

See example 2.


Example 1:

exti: interrupt-controller@40013c00 {
	compatible = "st,stm32-exti";
	interrupt-controller;
	#interrupt-cells = <2>;
	reg = <0x40013C00 0x400>;
	interrupts = <1>, <2>, <3>, <6>, <7>, <8>, <9>, <10>, <23>, <40>, <41>, <42>, <62>, <76>;
};

Example 2:

exti: interrupt-controller@5000d000 {
	compatible = "st,stm32mp1-exti", "syscon";
	interrupt-controller;
	#interrupt-cells = <2>;
	reg = <0x5000d000 0x400>;

	exti_pwr: exti-pwr {
		interrupt-controller;
		#interrupt-cells = <2>;
		interrupt-parent = <&pwr>;
		st,irq-number = <6>;
	};
};