gpio: add sl28cpld driver

The gpio block is part of the sl28cpld sl28cpld management controller.
There are three different flavors: the usual input and output where the
direction is configurable, but also input only and output only variants.

Signed-off-by: Michael Walle <michael@walle.cc>
[Rebased]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 8d0e47c..522dfc1 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -544,4 +544,10 @@
 	  are accessed using xilinx firmware. In modepin register, [3:0] bits
 	  set direction, [7:4] bits read IO, [11:8] bits set/clear IO.
 
+config SL28CPLD_GPIO
+	bool "Kontron sl28cpld GPIO driver"
+	depends on DM_GPIO && SL28CPLD
+	help
+	  Support GPIO access on Kontron sl28cpld board management controllers.
+
 endif