FdtNode::interrupts() can not handle ARM interrupt properties

[ravenexp]

On ARM, #interrupt-cells property value is usually 3:
https://www.kernel.org/doc/Documentation/devicetree/bindings/interrupt-controller/arm%2Cgic.txt.

This common case is not handled by the current method implementation:

fdt/src/node.rs

Lines 256 to 260 in 0c2fb5b

	let interrupt = match sizes {
	1 => stream.u32()?.get() as usize,
	2 => stream.u64()?.get() as usize,
	_ => return None,
	};

Also, interpreting the #interrupt-cells = <2> case as a single u64 interrupt number does not seem correct either,
because the Linux kernel docs say that those two cells encode entirely different things:

b) two cells
  ------------
  The #interrupt-cells property is set to 2 and the first cell defines the
  index of the interrupt within the controller, while the second cell is used
  to specify any of the following flags:

Source: https://www.kernel.org/doc/Documentation/devicetree/bindings/interrupt-controller/interrupts.txt

To handle all variants of interrupts correctly, this method should probably return an iterator over a custom Interrupt type,
just like FdtNode::reg() returns an iterator over MemoryRegion items.

[repnop]

Sorry for the long delay in response, but you're correct! I mainly wrote and tested all of this code for RISC-V, so its not something I caught, so I'll have this in mind for the set of improvements I'm planning on making here hopefully soon.