irqchip/apple-aic: Add support for the Apple Interrupt Controller

This is the root interrupt controller used on Apple ARM SoCs such as the
M1. This irqchip driver performs multiple functions:

* Handles both IRQs and FIQs

* Drives the AIC peripheral itself (which handles IRQs)

* Dispatches FIQs to downstream hard-wired clients (currently the ARM
  timer).

* Implements a virtual IPI multiplexer to funnel multiple Linux IPIs
  into a single hardware IPI
Reviewed-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>

MAINTAINERS

@@ -1647,6 +1647,8 @@ C:	irc://chat.freenode.net/asahi-dev
 T:	git https://github.com/AsahiLinux/linux.git
 F:	Documentation/devicetree/bindings/arm/apple.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml
+F:	drivers/irqchip/irq-apple-aic.c
+F:	include/dt-bindings/interrupt-controller/apple-aic.h
 
 ARM/ARTPEC MACHINE SUPPORT
 M:	Jesper Nilsson <jesper.nilsson@axis.com>

drivers/irqchip/Kconfig

@@ -577,4 +577,12 @@ config MST_IRQ
 	help
 	  Support MStar Interrupt Controller.
 
+config APPLE_AIC
+	bool "Apple Interrupt Controller (AIC)"
+	depends on ARM64
+	default ARCH_APPLE
+	help
+	  Support for the Apple Interrupt Controller found on Apple Silicon SoCs,
+	  such as the M1.
+
 endmenu

drivers/irqchip/Makefile

@@ -113,3 +113,4 @@ obj-$(CONFIG_LOONGSON_PCH_MSI)		+= irq-loongson-pch-msi.o
 obj-$(CONFIG_MST_IRQ)			+= irq-mst-intc.o
 obj-$(CONFIG_SL28CPLD_INTC)		+= irq-sl28cpld.o
 obj-$(CONFIG_MACH_REALTEK_RTL)		+= irq-realtek-rtl.o
+obj-$(CONFIG_APPLE_AIC)			+= irq-apple-aic.o

include/linux/cpuhotplug.h

@@ -100,6 +100,7 @@ enum cpuhp_state {
 	CPUHP_AP_CPU_PM_STARTING,
 	CPUHP_AP_IRQ_GIC_STARTING,
 	CPUHP_AP_IRQ_HIP04_STARTING,
+	CPUHP_AP_IRQ_APPLE_AIC_STARTING,
 	CPUHP_AP_IRQ_ARMADA_XP_STARTING,
 	CPUHP_AP_IRQ_BCM2836_STARTING,
 	CPUHP_AP_IRQ_MIPS_GIC_STARTING,