irqchip/irq-mvebu-sei: Add new driver for Marvell SEI

This is a cascaded interrupt controller in the AP806 GIC that collapses
SEIs (System Error Interrupt) coming from the AP and the CPs (through
the ICU).

The SEI handles up to 64 interrupts. The first 21 interrupts are wired
from the AP. The next 43 interrupts are from the CPs and are triggered
through MSI messages. To handle this complexity, the driver has to
declare to the upper layer: one IRQ domain for the wired interrupts,
one IRQ domain for the MSIs; and acts as a MSI controller ('parent')
by declaring an MSI domain.
Suggested-by: Haim Boot <hayim@marvell.com>
Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/Kconfig

@@ -310,6 +310,9 @@ config MVEBU_ODMI
 config MVEBU_PIC
 	bool
 
+config MVEBU_SEI
+        bool
+
 config LS_SCFG_MSI
 	def_bool y if SOC_LS1021A || ARCH_LAYERSCAPE
 	depends on PCI && PCI_MSI

drivers/irqchip/Makefile

@@ -76,6 +76,7 @@ obj-$(CONFIG_MVEBU_GICP)		+= irq-mvebu-gicp.o
 obj-$(CONFIG_MVEBU_ICU)			+= irq-mvebu-icu.o
 obj-$(CONFIG_MVEBU_ODMI)		+= irq-mvebu-odmi.o
 obj-$(CONFIG_MVEBU_PIC)			+= irq-mvebu-pic.o
+obj-$(CONFIG_MVEBU_SEI)			+= irq-mvebu-sei.o
 obj-$(CONFIG_LS_SCFG_MSI)		+= irq-ls-scfg-msi.o
 obj-$(CONFIG_EZNPS_GIC)			+= irq-eznps.o
 obj-$(CONFIG_ARCH_ASPEED)		+= irq-aspeed-vic.o irq-aspeed-i2c-ic.o

include/linux/irqdomain.h

@@ -75,6 +75,7 @@ struct irq_fwspec {
 enum irq_domain_bus_token {
 	DOMAIN_BUS_ANY		= 0,
 	DOMAIN_BUS_WIRED,
+	DOMAIN_BUS_GENERIC_MSI,
 	DOMAIN_BUS_PCI_MSI,
 	DOMAIN_BUS_PLATFORM_MSI,
 	DOMAIN_BUS_NEXUS,