dt-bindings: iio: adc: Add MAX1241 bindings

Add device-tree bindings documentation for the MAX1241 device driver.
Signed-off-by: Alexandru Lazar <alazar@startmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/maxim,max1241.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2020 Alexandru Lazar
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/maxim,max1241.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim MAX1241 12-bit, single-channel analog to digital converter
+
+maintainers:
+  - Alexandru Lazar <alazar@startmail.com>
+
+description: |
+  Bindings for the max1241 12-bit, single-channel ADC device. Datasheet
+  can be found at:
+    https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf
+
+properties:
+  compatible:
+    enum:
+      - maxim,max1241
+
+  reg:
+    maxItems: 1
+
+  vdd-supply:
+    description:
+      Device tree identifier of the regulator that powers the ADC.
+
+  vref-supply:
+    description:
+      Device tree identifier of the regulator that provides the external
+      reference voltage.
+
+  shutdown-gpios:
+    description:
+      GPIO spec for the GPIO pin connected to the ADC's /SHDN pin. If
+      specified, the /SHDN pin will be asserted between conversions,
+      thus enabling power-down mode.
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - vdd-supply
+  - vref-supply
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+        adc@0 {
+            compatible = "maxim,max1241";
+            reg = <0>;
+            vdd-supply = <&adc_vdd>;
+            vref-supply = <&adc_vref>;
+            spi-max-frequency = <1000000>;
+            shutdown-gpios = <&gpio 26 1>;
+        };
+    };