dm: gpio: Add driver for MPC85XX GPIO controller

This patch adds a driver for the built-in GPIO controller of the MPC85XX
SoC (probably supporting other PowerQUICC III SoCs as well).

Each GPIO bank is identified by its own entry in the device tree, i.e.

gpio-controller@fc00 {
      #gpio-cells = <2>;
      compatible = "fsl,pq3-gpio";
      reg = <0xfc00 0x100>
}

By default, each bank is assumed to have 32 GPIOs, but the ngpios
setting is honored, so the number of GPIOs for each bank in configurable
to match the actual GPIO count of the SoC (e.g. the 32/32/23 banks of
the P1022 SoC).

The usual functions of GPIO drivers (setting input/output mode and output
value setting) are supported.

The driver has been tested on MPC85XX, but it is likely that other
PowerQUICC III devices will work as well.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 93a7e8c..b674a47 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -173,4 +173,30 @@
 
 	  Now, max 24 bits chips and PCA953X compatible chips are
 	  supported
+
+config MPC85XX_GPIO
+	bool "Freescale MPC85XX GPIO driver"
+	depends on DM_GPIO
+	help
+	  This driver supports the built-in GPIO controller of MPC85XX CPUs.
+	  Each GPIO bank is identified by its own entry in the device tree,
+	  i.e.
+
+	  gpio-controller@fc00 {
+		#gpio-cells = <2>;
+		compatible = "fsl,pq3-gpio";
+		reg = <0xfc00 0x100>
+	  }
+
+	  By default, each bank is assumed to have 32 GPIOs, but the ngpios
+	  setting is honored, so the number of GPIOs for each bank is
+	  configurable to match the actual GPIO count of the SoC (e.g. the
+	  32/32/23 banks of the P1022 SoC).
+
+	  The standard functions of input/output mode, and output value setting
+	  are supported; the open-drain capability of the controller is not
+	  supported yet.
+
+	  The driver has been tested on MPC85XX, but it is likely that other
+	  PowerQUICC III devices will work as well.
 endmenu