[PATCH 3/6] irqdomain: add struct irq_hwcfg and helper functions

struct irq_hwcfg is used to describe hardware IPI setup. >From ThomasG suggestion, there's generic parts and a union of hardware specific part. Assuming that virq and hwirq are enough to describe different sort of hardwares as so far they are all that was needed, I'm hoping this implementation

[PATCH 3/6] irqdomain: add struct irq_hwcfg and helper functions

struct irq_hwcfg is used to describe hardware IPI setup. >From ThomasG suggestion, there's generic parts and a union of hardware specific part. Assuming that virq and hwirq are enough to describe different sort of hardwares as so far they are all that was needed, I'm hoping this implementation