Add a driver to read group of GPIO lines and provide its status as a
numerical value as input event to the system. This will help in
intefacing devices, that can be connected over GPIOs, that provide input
to the system by driving GPIO lines connected to them like a rotary dial
or a switch.

For example, a rotary switch can be connected to four GPIO lines. The
status of the GPIO lines reflect the actual position of the rotary
switch dial. For example, if dial points to 9, then the four GPIO lines
connected to the switch will read HLLH(0b'1001 = 9). This value
can be reported as an ABS_* event to the input subsystem.

Signed-off-by: Vignesh R <vigneshr@ti.com>
---
 .../devicetree/bindings/input/gpio-decoder.txt     |  23 ++++
 drivers/input/misc/Kconfig                         |  12 ++
 drivers/input/misc/Makefile                        |   1 +
 drivers/input/misc/gpio_decoder.c                  | 128 +++++++++++++++++++++
 4 files changed, 164 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/gpio-decoder.txt
 create mode 100644 drivers/input/misc/gpio_decoder.c

diff --git a/Documentation/devicetree/bindings/input/gpio-decoder.txt b/Documentation/devicetree/bindings/input/gpio-decoder.txt
new file mode 100644
index 000000000000..efd947f52cb3
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/gpio-decoder.txt

@@ -0,0 +1,23 @@
+* GPIO Decoder DT bindings
+
+Required Properties:
+- compatible: should be "gpio-decoder"
+- gpios: a spec of gpios (atleast two) to be decoded to a number with
+  first entry representing the MSB.
+
+Optional Properties:
+- gpio-decoder,max-value: Maximum possible value that can be reported by