mfd: simple-mfd-i2c: Add sl28cpld support

Add the core support for the board management controller found on the
SMARC-sAL28 board.

Also add a virtual symbol which pulls in the simple-mfd-i2c driver and
provide a common symbol on which the subdevice drivers can depend on.

At the moment, this controller is used on the Kontron SMARC-sAL28 board.

Signed-off-by: Michael Walle <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/Kconfig

···
 	  sub-devices represented by child nodes in Device Tree will be
 	  subsequently registered.
 
+config MFD_SL28CPLD
+	tristate "Kontron sl28cpld Board Management Controller"
+	select MFD_SIMPLE_MFD_I2C
+	help
+	  Say yes here to enable support for the Kontron sl28cpld board
+	  management controller.
+
+	  It can be found on the following boards:
+		* SMARC-sAL28
+
 config MFD_SM501
 	tristate "Silicon Motion SM501"
 	depends on HAS_DMA

drivers/mfd/simple-mfd-i2c.c

···
 }
 
 static const struct of_device_id simple_mfd_i2c_of_match[] = {
+	{ .compatible = "kontron,sl28cpld" },
 	{}
 };
 MODULE_DEVICE_TABLE(of, simple_mfd_i2c_of_match);