irqdomain: Add firmware info reporting interface

irqdomain: Add firmware info reporting interface

Add an irqdomain callback to report firmware-provided information that is
otherwise not available in a generic way. This is reported using a new data
structure (struct irq_fwspec_info).

This callback is optional and the only information that can be reported
currently is the affinity of an interrupt. However, the containing
structure is designed to be extensible, allowing other potentially relevant
information to be reported in the future.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Will Deacon <will@kernel.org>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20251020122944.3074811-2-maz@kernel.org