doc: add supported sysfs for max42500

Add documentation for supported ABI sysfs entries for MAX42500.

Signed-off-by: Kent Libetario <Kent.Libetario@analog.com>

Author: kentlibe

Documentation/hwmon/max42500-hwmon.rst

@@ -0,0 +1,135 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver max42500
+======================
+
+Supported chips:
+  * Analog Devices MAX42500
+
+    Prefix: 'max42500'
+
+    Addresses scanned: I2C 0x28 to 0x2B
+
+    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/max42500.pdf
+
+Author: Kent Libetario <Kent.Libetario@analog.com>
+
+Description
+-----------
+
+This driver supports hardware monitoring of MAX42500 power system with up
+to seven voltage monitor inputs. Each input has programmable overvoltage
+(OV) and undervoltage (UV) thresholds where two of the inputs support
+dynamic voltage scaling (DVS). Additionally, the MAX42500 features a
+programmable flexible power sequence recorder that stores timestamps
+separately. And also, the MAX42500 has a programmable challenge and
+response watchdog with a configurable RESET output.
+
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate the
+devices explicitly. Please see Documentation/i2c/instantiating-devices.rst
+for details.
+
+Due to its multi-functionality, the MAX42500 is split into three drivers:
+the mfd driver as the main device, and the hwmon and watchdog drivers as
+the sub-devices. The mfd driver is a client to the core driver and
+consumed by both the hwmon and watchdog drivers.
+
+Optionally, two power management GPIOs are provided by the mfd driver and
+consumed only by the hwmon sub-device driver. The pins are fixed-outputs
+to control the voltage monitor comparators and trigger the power sequence
+timestamp recording of the device. Please see the datasheet for details.
+
+For the two GPIO output pins to be consumed, the device tree will look
+like this:
+
+.. code-block::
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        poweroff-gpios
+        sleepoff-gpios
+
+        hwmon@28 {
+            compatible = "adi,max42500";
+            reg = <0x28>;
+        };
+    };
+
+Otherwise, the two pins maybe omitted in the device tree if unused.
+
+
+Platform data support
+---------------------
+
+The Hwmon driver supports standard Hwmon ABI driver and sysfs platform
+data. While the watchdog driver supports the standard watchdog ABI driver
+and sysfs platform data.
+
+
+Hwmon Sysfs entries
+-------------------
+
+The following attributes are supported. Limits are read-write; all other
+attributes are read-only.
+
+
+Chip
+~~~~
+
+======================= =======================================================
+chip_pec		 Enable or disable PEC: PECE bit in CONFIG1 register
+======================= =======================================================
+
+In
+~~
+
+======================= ======================================================
+in[1-7]_label		 "VMON[1-7]"
+in[1-7]_enable		 Enable or disable voltage monitors: VM1 to VM7 bits of
+			 VMON register
+in[1-5]_min		 Nominal Voltage set point: VIN1 to VIN5 registers
+in[1-5]_lcrit		 IN1-IN5 UV threshold: UV1 to UV5 nibbles of OVUV1 to
+			 OVUV5 registers
+in[6-7]_lcrit		 IN6-IN7 UV threshold: VINU6 to VINU7 registers
+in[1-5]_crit		 IN1-IN5 OV threshold: OV1 to OV5 nibbles of OVUV1 to
+			 OVUV5 registers
+in[6-7]_crit		 IN6-IN7 OV threshold: VINO6 to VINO7 registers
+in[1-7]_reset_history	 Enable or disable reset mapping: IN1 to IN7 bits of
+			 RSTMAP register
+======================= ======================================================
+
+Power
+~~~~~
+
+=============================== ===============================================
+power[1-7]_label		  "STATUS[1-7]"
+power_enable			  OFF comparator status: STATOFF register
+power_lcrit_alarm		  UV comparator status: STATUV register
+power_crit_alarm		  OV comparator status: STATOV register
+power[1-7]_average_interval_min  Power-Down sequence time-stamp: DTIME1 to
+				  DTIME7 registers
+power[1-7]_average_interval_max  Power-Up sequence time-stamp: UTIME1 to
+				  UTIME7 registers
+=============================== ===============================================
+
+
+Watchdog Sysfs entries
+----------------------
+
+======================= =======================================================
+start			 Enable the watchdog: WDEN bit of WDCFG2 register
+stop			 Disable the watchdog: WDEN bit of WDCFG2 register
+ping			 Set the watchdog key to the device: WDKEY register
+status			 Watchdog status: WDSTAT register
+set_timeout		 Watchdog Clock Divider: WDIV bits of WDCDIV register
+set_pretimeout		 First Update Extension: 1UD bit of WDCFG2 register
+restart 		 Reset Hold or Active Timeout: RHLD bits of RSTCTRL
+			 register
+======================= =======================================================
+
+..