dt-bindings: hwmon: ltc2991: add bindings

Add dt-bindings for ltc2991 octal i2c voltage, current and temperature
monitor.
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231026103413.27800-1-antoniu.miclaus@analog.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/adi,ltc2991.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+
+$id: http://devicetree.org/schemas/hwmon/adi,ltc2991.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices LTC2991 Octal I2C Voltage, Current and Temperature Monitor
+
+maintainers:
+  - Antoniu Miclaus <antoniu.miclaus@analog.com>
+
+description: |
+  The LTC2991 is used to monitor system temperatures, voltages and currents.
+  Through the I2C serial interface, the eight monitors can individually measure
+  supply voltages and can be paired for differential measurements of current
+  sense resistors or temperature sensing transistors.
+
+  Datasheet:
+    https://www.analog.com/en/products/ltc2991.html
+
+properties:
+  compatible:
+    const: adi,ltc2991
+
+  reg:
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  vcc-supply: true
+
+patternProperties:
+  "^channel@[0-3]$":
+    type: object
+    description:
+      Represents the differential/temperature channels.
+
+    properties:
+      reg:
+        description:
+          The channel number. LTC2991 can monitor 4 currents/temperatures.
+        items:
+          minimum: 0
+          maximum: 3
+
+      shunt-resistor-micro-ohms:
+        description:
+          The value of curent sense resistor in micro ohms. Pin configuration is
+          set for differential input pair.
+
+      adi,temperature-enable:
+        description:
+          Enables temperature readings. Pin configuration is set for remote
+          diode temperature measurement.
+        type: boolean
+
+    required:
+      - reg
+
+    allOf:
+      - if:
+          required:
+            - shunt-resistor-micro-ohms
+        then:
+          properties:
+            adi,temperature-enable: false
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - vcc-supply
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        hwmon@48 {
+            compatible = "adi,ltc2991";
+            reg = <0x48>;
+            vcc-supply = <&vcc>;
+        };
+    };
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        hwmon@48 {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            compatible = "adi,ltc2991";
+            reg = <0x48>;
+            vcc-supply = <&vcc>;
+
+            channel@0 {
+                    reg = <0x0>;
+                    shunt-resistor-micro-ohms = <100000>;
+            };
+
+            channel@1 {
+                    reg = <0x1>;
+                    shunt-resistor-micro-ohms = <100000>;
+            };
+
+            channel@2 {
+                    reg = <0x2>;
+                    adi,temperature-enable;
+            };
+
+            channel@3 {
+                    reg = <0x3>;
+                    adi,temperature-enable;
+            };
+        };
+    };
+...