dt-bindings: iio: resolver: add devicetree bindings for ad2s1210

This adds new DeviceTree bindings for the Analog Devices, Inc. AD2S1210
resolver-to-digital converter.
Co-developed-by: Apelete Seketeli <aseketeli@baylibre.com>
Signed-off-by: Apelete Seketeli <aseketeli@baylibre.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230929-ad2s1210-mainline-v3-1-fa4364281745@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/resolver/adi,ad2s1210.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/resolver/adi,ad2s1210.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD2S1210 Resolver-to-Digital Converter
+
+maintainers:
+  - Michael Hennerich <michael.hennerich@analog.com>
+
+description: |
+  The AD2S1210 is a complete 10-bit to 16-bit resolution tracking
+  resolver-to-digital converter, integrating an on-board programmable
+  sinusoidal oscillator that provides sine wave excitation for
+  resolvers.
+
+  The AD2S1210 allows the user to read the angular position or the
+  angular velocity data directly from the parallel outputs or through
+  the serial interface.
+
+  The mode of operation of the communication channel (parallel or serial) is
+  selected by the A0 and A1 input pins. In normal mode, data is latched by
+  toggling the SAMPLE line and can then be read directly. In configuration mode,
+  data is read or written using a register access scheme (address byte with
+  read/write flag and data byte).
+
+    A1  A0  Result
+     0   0  Normal mode - position output
+     0   1  Normal mode - velocity output
+     1   0  Reserved
+     1   1  Configuration mode
+
+  In normal mode, the resolution of the digital output is selected using
+  the RES0 and RES1 input pins. In configuration mode, the resolution is
+  selected by setting the RES0 and RES1 bits in the control register.
+
+  RES1  RES0  Resolution (Bits)
+     0     0  10
+     0     1  12
+     1     0  14
+     1     1  16
+
+  Note on SPI connections: The CS line on the AD2S1210 should hard-wired to
+  logic low and the WR/FSYNC line on the AD2S1210 should be connected to the
+  SPI CSn output of the SPI controller.
+
+  Datasheet:
+  https://www.analog.com/media/en/technical-documentation/data-sheets/ad2s1210.pdf
+
+properties:
+  compatible:
+    const: adi,ad2s1210
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 25000000
+
+  spi-cpha: true
+
+  avdd-supply:
+    description:
+      A 4.75 to 5.25 V regulator that powers the Analog Supply Voltage (AVDD)
+      pin.
+
+  dvdd-supply:
+    description:
+      A 4.75 to 5.25 V regulator that powers the Digital Supply Voltage (DVDD)
+      pin.
+
+  vdrive-supply:
+    description:
+      A 2.3 to 5.25 V regulator that powers the Logic Power Supply Input
+      (VDrive) pin.
+
+  clocks:
+    maxItems: 1
+    description: External oscillator clock (CLKIN).
+
+  reset-gpios:
+    description:
+      GPIO connected to the /RESET pin. As the line needs to be low for the
+      reset to be active, it should be configured as GPIO_ACTIVE_LOW.
+    maxItems: 1
+
+  sample-gpios:
+    description:
+      GPIO connected to the /SAMPLE pin. As the line needs to be low to trigger
+      a sample, it should be configured as GPIO_ACTIVE_LOW.
+    maxItems: 1
+
+  mode-gpios:
+    description:
+      GPIO lines connected to the A0 and A1 pins. These pins select the data
+      transfer mode.
+    minItems: 2
+    maxItems: 2
+
+  resolution-gpios:
+    description:
+      GPIO lines connected to the RES0 and RES1 pins. These pins select the
+      resolution of the digital output. If omitted, it is assumed that the
+      RES0 and RES1 pins are hard-wired to match the assigned-resolution-bits
+      property.
+    minItems: 2
+    maxItems: 2
+
+  fault-gpios:
+    description:
+      GPIO lines connected to the LOT and DOS pins. These pins combined indicate
+      the type of fault present, if any. As these pins a pulled low to indicate
+      a fault condition, they should be configured as GPIO_ACTIVE_LOW.
+    minItems: 2
+    maxItems: 2
+
+  adi,fixed-mode:
+    description:
+      This is used to indicate the selected mode if A0 and A1 are hard-wired
+      instead of connected to GPIOS (i.e. mode-gpios is omitted).
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [config, velocity, position]
+
+  assigned-resolution-bits:
+    description:
+      Resolution of the digital output required by the application. This
+      determines the precision of the angle and/or the maximum speed that can
+      be measured. If resolution-gpios is omitted, it is assumed that RES0 and
+      RES1 are hard-wired to match this value.
+    enum: [10, 12, 14, 16]
+
+required:
+  - compatible
+  - reg
+  - spi-cpha
+  - avdd-supply
+  - dvdd-supply
+  - vdrive-supply
+  - clocks
+  - sample-gpios
+  - assigned-resolution-bits
+
+oneOf:
+  - required:
+      - mode-gpios
+  - required:
+      - adi,fixed-mode
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        resolver@0 {
+            compatible = "adi,ad2s1210";
+            reg = <0>;
+            spi-max-frequency = <20000000>;
+            spi-cpha;
+            avdd-supply = <&avdd_regulator>;
+            dvdd-supply = <&dvdd_regulator>;
+            vdrive-supply = <&vdrive_regulator>;
+            clocks = <&ext_osc>;
+            sample-gpios = <&gpio0 90 GPIO_ACTIVE_LOW>;
+            mode-gpios = <&gpio0 86 0>, <&gpio0 87 0>;
+            resolution-gpios = <&gpio0 88 0>, <&gpio0 89 0>;
+            assigned-resolution-bits = <16>;
+        };
+    };