iio: adc: Device tree improvements for MAX22530-MAX22532

Improve initial DT Overlay for MAX22530-MAX22532.
Add MAX22530-MAX22532 device tree documentation.

Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>

Author: psychild

Documentation/devicetree/bindings/iio/adc/adi,max22531.yaml

@@ -0,0 +1,66 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2025 Abhinav Jain
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,max22531.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX22530-MAX22532 12-bit Field Isolated ADCs
+
+maintainers:
+  - Abhinav Jain <jain.abhinav177@gmail.com>
+
+description:
+  Bindings for the Analog Devices Max22530-MAX22532 Field-Side Self-Powered,
+  4-Channel, 12-bit, Isolated ADCs.
+
+  Datasheet can be found here
+    https://www.analog.com/media/en/technical-documentation/data-sheets/max22530-max22532.pdf
+
+properties:
+  compatible:
+    enum:
+      - adi,max22530
+      - adi,max22531
+      - adi,max22532
+
+  reg:
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  vddl-supply:
+    description:
+      Logic power supply.
+
+  vddpl-supply:
+    description:
+      Isolated DC-DC converter power supply.
+
+  required:
+    - compatible
+    - reg
+    - vddl-supply
+    - vddpl-supply
+
+  allOf:
+    - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+  examples:
+    - |
+      spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        max22531: adc@0 {
+          compatible = "adi,max22531";
+          reg = <0>;
+          spi-max-frequency = <5000000>;
+          vddl-supply = <&vddl>;
+          vddpl-supply = <&vddpl>;
+        };
+      };

arch/arm/boot/dts/overlays/rpi-max22531-overlay.dts

@@ -7,11 +7,20 @@
 /plugin/;
 
 / {
-	compatible = "brcm,bcm2835-spi", "brcm,bcm2711";
+	compatible = "brcm,bcm2835", "brcm,bcm2711", "brcm,bcm2712";
 
-	reg_vdd: regulator {
+	vddl_1v8: fixedregulator@0 {
 		compatible = "regulator-fixed";
-		regulator-name = "vdd";
+		regulator-name = "Power Input for the Logic-Side";
+		regulator-min-microvolt = <1800000>;
+		regulator-max-microvolt = <1800000>;
+		regulator-boot-on;
+		regulator-always-on;
+	};
+
+	vddpl_3v3: fixedregulator@1 {
+		compatible = "regulator-fixed";
+		regulator-name = "Power Input for the Isolated DC-DC Converter";
 		regulator-min-microvolt = <3300000>;
 		regulator-max-microvolt = <3300000>;
 		regulator-boot-on;
@@ -23,10 +32,10 @@
 	status = "okay";
 
 	max22531@0 {
-		compatible = "maxim,max22531";
+		compatible = "adi,max22531";
 		reg = <0>;	/* Using CS0 on spi0 */
-		spi-max-frequency = <10000000>;
-		vref-supply = <&reg_vdd>;
-
+		spi-max-frequency = <5000000>;
+		vddl-supply = <&vddl_1v8>;
+		vddpl-supply = <&vddpl_3v3>;
 	};
 };