MAXIM Semiconductor's PMIC, MAX77620/MAX20024 has 8 GPIO
pins. It also supports interrupts from these pins.

Add GPIO driver for these pins to control via GPIO APIs.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Chaitanya Bandi <redacted>
---
Changes from V1:
- Use the gpiochip_add_data and get the chip data from core APIs.
- Cleanups based on comment received on mfd/rtc.
- Avoid duplication on error message.

Changes form V2:
- Run coccicheck and checkpatch in strict mode for the alignment.
- update based on api changes from core.

Changes from V3: 
- Change all sys initcall to module driver.
- change the max77620_read argument to unisgned int from u8.

Changes from V4: 
- Added DT binding document as devicetree/bindings/gpio/gpio-max77620.txt

 .../devicetree/bindings/gpio/gpio-max77620.txt     |  25 ++
 drivers/gpio/Kconfig                               |   9 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-max77620.c                       | 292 +++++++++++++++++++++
 4 files changed, 327 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-max77620.txt
 create mode 100644 drivers/gpio/gpio-max77620.c

diff --git a/Documentation/devicetree/bindings/gpio/gpio-max77620.txt b/Documentation/devicetree/bindings/gpio/gpio-max77620.txt
new file mode 100644
index 0000000..410e716
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-max77620.txt

@@ -0,0 +1,25 @@
+GPIO driver for MAX77620 Power management IC from Maxim Semiconductor.
+
+Device has 8 GPIO pins which can be configured as GPIO as well as the
+special IO functions.
+
+Required properties:
+-------------------
+- gpio-controller : 	Marks the device node as a gpio controller.
+- #gpio-cells : 	Should be two.  The first cell is the pin number and
+			the second cell is used to specify the gpio polarity:
+				0 = active high
+				1 = active low
+For more details, please refer generic GPIO DT binding document
+<devicetree/bindings/gpio/gpio.txt>.