mfd: Add support for the MediaTek MT6397 PMIC

This adds support for the MediaTek MT6397 PMIC. This is a
multifunction device with the following sub modules:

- Regulator
- RTC
- Audio codec
- GPIO
- Clock

It is interfaced to the host controller using SPI interface by a proprietary
hardware called PMIC wrapper or pwrap. MT6397 MFD is a child device of the
pwrap.

Signed-off-by: Flora Fu, MediaTek
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index b5fb03c..c602f74 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -503,6 +503,16 @@
 	  additional drivers must be enabled in order to use the functionality
 	  of the device.
 
+config MFD_MT6397
+	tristate "MediaTek MT6397 PMIC Support"
+	select MFD_CORE
+	select IRQ_DOMAIN
+	help
+	  Say yes here to add support for MediaTek MT6397 PMIC. This is
+	  a Power Management IC. This driver provides common support for
+	  accessing the device; additional drivers must be enabled in order
+	  to use the functionality of the device.
+
 config MFD_MENF21BMC
 	tristate "MEN 14F021P00 Board Management Controller Support"
 	depends on I2C