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 UCLASS_PINCTRL and UCLASS_GPIO.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/drivers/pinctrl/Kconfig b/drivers/pinctrl/Kconfig
index be709f7..a0ac167 100644
--- a/drivers/pinctrl/Kconfig
+++ b/drivers/pinctrl/Kconfig
@@ -209,6 +209,25 @@
 	  the GPIO definitions and pin control functions for each available
 	  multiplex function.
 
+config PINCTRL_STMFX
+	bool "STMicroelectronics STMFX I2C GPIO expander pinctrl driver"
+	depends on DM && PINCTRL_FULL
+	help
+	  I2C driver for STMicroelectronics Multi-Function eXpander (STMFX)
+	  GPIO expander.
+	  Supports pin multiplexing control on stm32 SoCs.
+
+	  The driver is controlled by a device tree node which contains both
+	  the GPIO definitions and pin control functions for each available
+	  multiplex function.
+
+config SPL_PINCTRL_STMFX
+	bool "STMicroelectronics STMFX I2C GPIO expander pinctrl driver in SPL"
+	depends on SPL_PINCTRL_FULL
+	help
+	  This option is an SPL-variant of the SPL_PINCTRL_STMFX option.
+	  See the help of PINCTRL_STMFX for details.
+
 config ASPEED_AST2500_PINCTRL
   bool "Aspeed AST2500 pin control driver"
   depends on DM && PINCTRL_GENERIC && ASPEED_AST2500