dt-bindings:iio:adc:maxim,max1027: Pull out to separate binding doc.

The afe/voltage-divider.yaml example uses this device with 2 properties
not provided by trivial-devices.yaml (spi-max-frequency and #io-channel-cells)

Solve that by creating a more specific binding doc.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Philippe Reynes <tremyfr@yahoo.fr>
Link: https://lore.kernel.org/r/20201031181242.742301-8-jic23@kernel.org

Documentation/devicetree/bindings/iio/adc/maxim,max1027.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/maxim,max1027.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Maxim MAX1027 and similar ADCs
+
+maintainers:
+  - Miquel Raynal <miquel.raynal@bootlin.com>
+  - Philippe Reynes <tremyfr@yahoo.fr>
+
+description: |
+  300ks/s SPI ADCs with temperature sensors.
+
+properties:
+  compatible:
+    enum:
+        # 10-bit 8 channels
+      - maxim,max1027
+        # 10-bit 12 channels
+      - maxim,max1029
+        # 10-bit 16 channels
+      - maxim,max1031
+         # 12-bit 8 channels
+      - maxim,max1227
+         # 12-bit 12 channels
+      - maxim,max1229
+         # 12-bit 16 channels
+      - maxim,max1231
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 10000000
+
+  "#io-channel-cells":
+    const: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi {
+       #address-cells = <1>;
+       #size-cells = <0>;
+        maxadc: adc@0 {
+            compatible = "maxim,max1027";
+            reg = <0>;
+            #io-channel-cells = <1>;
+            interrupt-parent = <&gpio5>;
+            interrupts = <15 IRQ_TYPE_EDGE_RISING>;
+            spi-max-frequency = <1000000>;
+        };
+    };
+...

Documentation/devicetree/bindings/trivial-devices.yaml

@@ -122,18 +122,6 @@ properties:
           - maxim,ds1803-050
             # 100 kOhm digital potentiometer with I2C interface
           - maxim,ds1803-100
-            # 10-bit 8 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1027
-            # 10-bit 12 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1029
-            # 10-bit 16 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1031
-            # 12-bit 8 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1227
-            # 12-bit 12 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1229
-            # 12-bit 16 channels 300ks/s SPI ADC with temperature sensor
-          - maxim,max1231
             # Low-Power, 4-/12-Channel, 2-Wire Serial, 12-Bit ADCs
           - maxim,max1237
             # 10-bit 10 kOhm linear programable voltage divider