dt-bindings: iio: dac: adi-axi-dac: add ad3552r axi variant

Add a new compatible and related bindigns for the fpga-based
"ad3552r" AXI IP core, a variant of the generic AXI DAC IP.

The AXI "ad3552r" IP is a very similar HDL (fpga) variant of the
generic AXI "DAC" IP, intended to control ad3552r and similar chips,
mainly to reach high speed transfer rates using a QSPI DDR
(dobule-data-rate) interface.

The ad3552r device is defined as a child of the AXI DAC, that in
this case is acting as an SPI controller.

Note, #io-backend is present because it is possible (in theory anyway)
to use a separate controller for the control path than that used
for the datapath.

Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20241028-wip-bl-ad3552r-axi-v0-iio-testing-v9-2-f6960b4f9719@kernel-space.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml

@@ -19,11 +19,13 @@ description: |
   memory via DMA into the DAC.
 
   https://wiki.analog.com/resources/fpga/docs/axi_dac_ip
+  https://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html
 
 properties:
   compatible:
     enum:
       - adi,axi-dac-9.1.b
+      - adi,axi-ad3552r
 
   reg:
     maxItems: 1
@@ -36,7 +38,14 @@ properties:
       - const: tx
 
   clocks:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
+
+  clock-names:
+    items:
+      - const: s_axi_aclk
+      - const: dac_clk
+    minItems: 1
 
   '#io-backend-cells':
     const: 0
@@ -47,7 +56,29 @@ required:
   - reg
   - clocks
 
-additionalProperties: false
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: adi,axi-ad3552r
+    then:
+      $ref: /schemas/spi/spi-controller.yaml#
+      properties:
+        clocks:
+          minItems: 2
+        clock-names:
+          minItems: 2
+      required:
+        - clock-names
+    else:
+      properties:
+        clocks:
+          maxItems: 1
+        clock-names:
+          maxItems: 1
+
+unevaluatedProperties: false
 
 examples:
   - |
@@ -57,6 +88,38 @@ examples:
         dmas = <&tx_dma 0>;
         dma-names = "tx";
         #io-backend-cells = <0>;
-        clocks = <&axi_clk>;
+        clocks = <&clkc 15>;
+        clock-names = "s_axi_aclk";
+    };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    axi_dac: spi@44a70000 {
+        compatible = "adi,axi-ad3552r";
+        reg = <0x44a70000 0x1000>;
+        dmas = <&dac_tx_dma 0>;
+        dma-names = "tx";
+        #io-backend-cells = <0>;
+        clocks = <&clkc 15>, <&ref_clk>;
+        clock-names = "s_axi_aclk", "dac_clk";
+
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        dac@0 {
+            compatible = "adi,ad3552r";
+            reg = <0>;
+            reset-gpios = <&gpio0 92 GPIO_ACTIVE_HIGH>;
+            io-backends = <&axi_dac>;
+            spi-max-frequency = <20000000>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            channel@0 {
+                reg = <0>;
+                adi,output-range-microvolt = <(-10000000) (10000000)>;
+            };
+        };
     };
 ...