gpio: Add Spreadtrum EIC driver support

The Spreadtrum digital-chip EIC controller has 4 sub-modules: debounce EIC,
latch EIC, async EIC and sync EIC, and each sub-module can has multiple
banks and each bank contains 8 EICs.

Each EIC can only be used as input mode, and has the capability to trigger
interrupts when detecting input signals.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -170,6 +170,14 @@ config GPIO_DWAPB
 	  Say Y or M here to build support for the Synopsys DesignWare APB
 	  GPIO block.
 
+config GPIO_EIC_SPRD
+	tristate "Spreadtrum EIC support"
+	depends on ARCH_SPRD || COMPILE_TEST
+	depends on OF_GPIO
+	select GPIOLIB_IRQCHIP
+	help
+	  Say yes here to support Spreadtrum EIC device.
+
 config GPIO_EM
 	tristate "Emma Mobile GPIO"
 	depends on (ARCH_EMEV2 || COMPILE_TEST) && OF_GPIO

drivers/gpio/Makefile

@@ -45,6 +45,7 @@ obj-$(CONFIG_GPIO_DA9055)	+= gpio-da9055.o
 obj-$(CONFIG_GPIO_DAVINCI)	+= gpio-davinci.o
 obj-$(CONFIG_GPIO_DLN2)		+= gpio-dln2.o
 obj-$(CONFIG_GPIO_DWAPB)	+= gpio-dwapb.o
+obj-$(CONFIG_GPIO_EIC_SPRD)	+= gpio-eic-sprd.o
 obj-$(CONFIG_GPIO_EM)		+= gpio-em.o
 obj-$(CONFIG_GPIO_EP93XX)	+= gpio-ep93xx.o
 obj-$(CONFIG_GPIO_ETRAXFS)	+= gpio-etraxfs.o