Extcon: add MAX8997 extcon driver

This patch add extcon-max8997 driver to support the muic feature
of Maxim max8997 by using Extcon framework.

The extcon-max8997 driver is implemented based on 'drivers/misc/
max8997-muic.c' and then use Extcon interface instead of callback
function in struct max8997_muic_platform_data to notify cable state
of notifee which want to know always newly cable state when external
connector(e.g., USB, TA, JIG) is attached or detached.

v1
- Use Extcon interface to notify cable state of notifee instead of
 callback function when external connector is attached or detached.
- Bug fix of getting platform_data for irq_base value.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/extcon/Kconfig

@@ -21,4 +21,12 @@ config EXTCON_GPIO
 	  Say Y here to enable GPIO based extcon support. Note that GPIO
 	  extcon supports single state per extcon instance.
 
+config EXTCON_MAX8997
+	tristate "MAX8997 EXTCON Support"
+	depends on MFD_MAX8997
+	help
+	  If you say yes here you get support for the MUIC device of
+	  Maxim MAX8997 PMIC. The MAX8997 MUIC is a USB port accessory
+	  detector and switch.
+
 endif # MULTISTATE_SWITCH

drivers/extcon/Makefile

@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_EXTCON)		+= extcon_class.o
 obj-$(CONFIG_EXTCON_GPIO)	+= extcon_gpio.o
+obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o