hwmon: (pmbus/isl68137) Add driver for Intersil ISL68137 PWM Controller

Intersil ISL68137 is a digital output 7-phase configurable PWM
controller with an AVSBus interface.

Signed-off-by: Maxim Sloyko <maxims@google.com>
Signed-off-by: Robert Lippert <rlippert@google.com>
Signed-off-by: Patrick Venture <venture@google.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/isl68137

@@ -0,0 +1,72 @@
+Kernel driver isl68137
+======================
+
+Supported chips:
+  * Intersil ISL68137
+    Prefix: 'isl68137'
+    Addresses scanned: -
+    Datasheet: Publicly available at the Intersil website
+      https://www.intersil.com/content/dam/Intersil/documents/isl6/isl68137.pdf
+
+Authors:
+        Maxim Sloyko <maxims@google.com>
+        Robert Lippert <rlippert@google.com>
+        Patrick Venture <venture@google.com>
+
+Description
+-----------
+
+Intersil ISL68137 is a digital output 7-phase configurable PWM
+controller with an AVSBus interface.
+
+Usage Notes
+-----------
+
+This driver does not probe for PMBus devices. You will have to instantiate
+devices explicitly.
+
+The ISL68137 AVS operation mode must be enabled/disabled at runtime.
+
+Beyond the normal sysfs pmbus attributes, the driver exposes a control attribute.
+
+Additional Sysfs attributes
+---------------------------
+
+avs(0|1)_enable		Controls the AVS state of each rail.
+
+curr1_label		"iin"
+curr1_input		Measured input current
+curr1_crit		Critical maximum current
+curr1_crit_alarm	Current critical high alarm
+
+curr[2-3]_label		"iout[1-2]"
+curr[2-3]_input		Measured output current
+curr[2-3]_crit		Critical maximum current
+curr[2-3]_crit_alarm	Current critical high alarm
+
+in1_label		"vin"
+in1_input		Measured input voltage
+in1_lcrit		Critical minimum input voltage
+in1_lcrit_alarm		Input voltage critical low alarm
+in1_crit		Critical maximum input voltage
+in1_crit_alarm		Input voltage critical high alarm
+
+in[2-3]_label		"vout[1-2]"
+in[2-3]_input		Measured output voltage
+in[2-3]_lcrit		Critical minimum output voltage
+in[2-3]_lcrit_alarm	Output voltage critical low alarm
+in[2-3]_crit		Critical maximum output voltage
+in[2-3]_crit_alarm	Output voltage critical high alarm
+
+power1_label		"pin"
+power1_input		Measured input power
+power1_alarm		Input power high alarm
+
+power[2-3]_label	"pout[1-2]"
+power[2-3]_input	Measured output power
+
+temp[1-3]_input		Measured temperature
+temp[1-3]_crit		Critical high temperature
+temp[1-3]_crit_alarm	Chip temperature critical high alarm
+temp[1-3]_max		Maximum temperature
+temp[1-3]_max_alarm	Chip temperature high alarm