gpio: uniphier: add UniPhier GPIO controller driver

This GPIO controller is used on UniPhier SoC family.

It also serves as an interrupt controller, but interrupt signals are
just delivered to the parent irqchip without any latching or OR'ing.
This type of hardware can be well described with hierarchy IRQ domain.

One unfortunate thing for this device is that the interrupt mapping to
the interrupt parent is not contiguous.

I asked how DT can describe interrupt mapping between two irqchips [1],
but I could not find a good solution (at least in the framework level).
In fact, irqchip drivers using hierarchy domain generally hard-code the
DT binding of their parent.

After tackling on several approaches such as hard-code of hwirqs,
irq_domain_push_irq(), I ended up with a vendor specific property.
If we come up with a good idea to support this in the framework, we
can migrate over to it, but we can live with a driver-level solution
for now.

[1] https://lkml.org/lkml/2017/7/6/758

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

MAINTAINERS

@@ -2025,6 +2025,7 @@ F:	arch/arm/mm/cache-uniphier.c
 F:	arch/arm64/boot/dts/socionext/
 F:	drivers/bus/uniphier-system-bus.c
 F:	drivers/clk/uniphier/
+F:	drivers/gpio/gpio-uniphier.c
 F:	drivers/i2c/busses/i2c-uniphier*
 F:	drivers/irqchip/irq-uniphier-aidet.c
 F:	drivers/pinctrl/uniphier/

drivers/gpio/Kconfig

@@ -474,6 +474,14 @@ config GPIO_TZ1090_PDC
 	help
 	  Say yes here to support Toumaz Xenif TZ1090 PDC GPIOs.
 
+config GPIO_UNIPHIER
+	tristate "UniPhier GPIO support"
+	depends on ARCH_UNIPHIER || COMPILE_TEST
+	depends on OF_GPIO
+	select IRQ_DOMAIN_HIERARCHY
+	help
+	  Say yes here to support UniPhier GPIOs.
+
 config GPIO_VF610
 	def_bool y
 	depends on ARCH_MXC && SOC_VF610

drivers/gpio/Makefile

@@ -132,6 +132,7 @@ obj-$(CONFIG_GPIO_TWL6040)	+= gpio-twl6040.o
 obj-$(CONFIG_GPIO_TZ1090)	+= gpio-tz1090.o
 obj-$(CONFIG_GPIO_TZ1090_PDC)	+= gpio-tz1090-pdc.o
 obj-$(CONFIG_GPIO_UCB1400)	+= gpio-ucb1400.o
+obj-$(CONFIG_GPIO_UNIPHIER)	+= gpio-uniphier.o
 obj-$(CONFIG_GPIO_VF610)	+= gpio-vf610.o
 obj-$(CONFIG_GPIO_VIPERBOARD)	+= gpio-viperboard.o
 obj-$(CONFIG_GPIO_VR41XX)	+= gpio-vr41xx.o