DT enjoys a rather nice probing infrastructure for irqchips, while
ACPI is so far stuck into a very distant past.

This patch introduces a declarative API, allowing irqchips to be
self-contained and be called when a particular entry is matched
in the MADT table.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>