pinctrl: Add STMFX GPIO expander Pinctrl/GPIO driver

This patch adds pinctrl/GPIO driver for STMicroelectronics
Multi-Function eXpander (STMFX) GPIO expander.
STMFX is an I2C slave controller, offering up to 24 GPIOs.
The driver relies on generic pin config interface to configure the GPIOs.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index 2764d71..ab2eab7 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -265,6 +265,18 @@
 	select PINCONF
 	select GPIOLIB_IRQCHIP
 
+config PINCTRL_STMFX
+	tristate "STMicroelectronics STMFX GPIO expander pinctrl driver"
+	select GENERIC_PINCONF
+	select GPIOLIB_IRQCHIP
+	select MFD_STMFX
+	help
+	  Driver for STMicroelectronics Multi-Function eXpander (STMFX)
+	  GPIO expander.
+	  This provides a GPIO interface supporting inputs and outputs,
+	  and configuring push-pull, open-drain, and can also be used as
+	  interrupt-controller.
+
 config PINCTRL_U300
 	bool "U300 pin controller driver"
 	depends on ARCH_U300