drivers: dac: dac_ad569x: Support for AD569x DACs.

Added support for Analog Devices AD5691 / AD5692 / AD5693 DACs.

Signed-off-by: Jan Kubiznak <jan.kubiznak@deveritec.com>

dts/bindings/dac/adi,ad5691.yaml

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+# Copyright (c) 2024 Jan Kubiznak <jan.kubiznak@deveritec.com>
+# SPDX-License-Identifier: Apache-2.0
+
+description: Driver for AD5691 (12-bit) DAC.
+
+compatible: "adi,ad5691"
+
+include: adi,ad569x-base.yaml

dts/bindings/dac/adi,ad5692.yaml

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+# Copyright (c) 2024 Jan Kubiznak <jan.kubiznak@deveritec.com>
+# SPDX-License-Identifier: Apache-2.0
+
+description: Driver for AD5692 (14-bit) DAC.
+
+compatible: "adi,ad5692"
+
+include: adi,ad569x-base.yaml

dts/bindings/dac/adi,ad5693.yaml

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+# Copyright (c) 2024 Jan Kubiznak <jan.kubiznak@deveritec.com>
+# SPDX-License-Identifier: Apache-2.0
+
+description: Driver for AD5693 (16-bit) DAC.
+
+compatible: "adi,ad5693"
+
+include: adi,ad569x-base.yaml

dts/bindings/dac/adi,ad569x-base.yaml

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+# Copyright (c) 2024 Jan Kubiznak <jan.kubiznak@deveritec.com>
+# SPDX-License-Identifier: Apache-2.0
+
+include: [dac-controller.yaml]
+
+properties:
+  "#io-channel-cells":
+    const: 1
+
+  resolution:
+    type: int
+    required: true
+    description: DAC resolution.
+
+  voltage-reference-mv:
+    type: int
+    required: true
+    description: DAC reference voltage in mV.
+
+  voltage-reference:
+    type: string
+    default: "internal"
+    enum:
+      - "internal"
+      - "external"
+    description: |
+      DAC voltage reference select.
+      - Internal voltage reference - 2.5V (reg: 0).
+      - External voltage reference (reg: 1).
+      The default corresponds to the reset value of the register field.
+
+  gain:
+    type: string
+    default: "gain-1"
+    enum:
+      - "gain-1"
+      - "gain-2"
+    description: |
+      Gain selection bit.
+      - Gain of 1 (reg: 0).
+      - Gain of 2 (reg: 1).
+      The default corresponds to the reset value of the register field.
+
+  power-down-mode:
+    type: string
+    default: "normal"
+    enum:
+      - "normal"
+      - "power-down-1k"
+      - "power-down-100k"
+      - "power-down-3-state"
+    description: |
+      Power-down mode select.
+      - Normal mode (reg: 0).
+      - 1 kOhm output impedance (reg: 1).
+      - 100 kOhm output impedance (reg: 2).
+      - Three-state output impedance (reg: 3).
+      The default corresponds to the reset value of the register field.
+
+io-channel-cells:
+  - output