gpio: nuvoton: Add Nuvoton NPCM sgpio driver

Add Nuvoton BMC NPCM7xx/NPCM8xx sgpio driver support.
Nuvoton NPCM SGPIO module is combine serial to parallel IC (HC595)
and parallel to serial IC (HC165), and use APB3 clock to control it.
This interface has 4 pins  (D_out , D_in, S_CLK, LDSH).
BMC can use this driver to increase 64 GPI pins and 64 GPO pins to use.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/Kconfig

@@ -478,6 +478,13 @@ config GPIO_MXS
 	select GPIO_GENERIC
 	select GENERIC_IRQ_CHIP
 
+config GPIO_NPCM_SGPIO
+	bool "Nuvoton SGPIO support"
+	depends on ARCH_NPCM || COMPILE_TEST
+	select GPIOLIB_IRQCHIP
+	help
+	  Say Y here to support Nuvoton NPCM7XX/NPCM8XX SGPIO functionality.
+
 config GPIO_OCTEON
 	tristate "Cavium OCTEON GPIO"
 	depends on CAVIUM_OCTEON_SOC

drivers/gpio/Makefile

@@ -116,6 +116,7 @@ obj-$(CONFIG_GPIO_MT7621)		+= gpio-mt7621.o
 obj-$(CONFIG_GPIO_MVEBU)		+= gpio-mvebu.o
 obj-$(CONFIG_GPIO_MXC)			+= gpio-mxc.o
 obj-$(CONFIG_GPIO_MXS)			+= gpio-mxs.o
+obj-$(CONFIG_GPIO_NPCM_SGPIO)		+= gpio-npcm-sgpio.o
 obj-$(CONFIG_GPIO_OCTEON)		+= gpio-octeon.o
 obj-$(CONFIG_GPIO_OMAP)			+= gpio-omap.o
 obj-$(CONFIG_GPIO_PALMAS)		+= gpio-palmas.o