drivers: adc: add max1125x driver

This adds support for the max1125x (max11254, max11254)
family of spi adc devices.

Signed-off-by: Mustafa Abdullah Kus <mustafa.kus@sparsetechnology.com>

dts/bindings/adc/maxim,max11253.yaml

@@ -0,0 +1,5 @@
+description: Maxim Integrated MAX11253 SPI ADC
+
+compatible: "maxim,max11253"
+
+include: maxim,max1125x-base.yaml

dts/bindings/adc/maxim,max11254.yaml

@@ -0,0 +1,5 @@
+description: Maxim Integrated MAX11254 SPI ADC
+
+compatible: "maxim,max11254"
+
+include: maxim,max1125x-base.yaml

dts/bindings/adc/maxim,max1125x-base.yaml

@@ -0,0 +1,36 @@
+# Common fields for Analog Devices MAX1125x
+
+include: [adc-controller.yaml, spi-device.yaml]
+
+properties:
+  "#io-channel-cells":
+    const: 1
+  gpio0-enable:
+    type: boolean
+    description: this option for gpio0 enable or disable
+  gpio1-enable:
+    type: boolean
+    description: this option for gpio1 enable or disable
+  gpio0-direction:
+    type: boolean
+    description: this option for gpio0 direction enable for input, disable for output
+  gpio1-direction:
+    type: boolean
+    description: this option for gpio0 direction enable for input, disable for output
+  gpo0-enable:
+    type: boolean
+    description: this option for gpo0 enable or disable
+  gpo1-enable:
+    type: boolean
+    description: this option for gpo1 enable or disable
+  drdy-gpios:
+    type: phandle-array
+    required: true
+    description: |
+      gpio for data ready, becomes active when a conversion result is ready
+  self-calibration:
+    type: boolean
+    description: start self calibration during channel setup
+
+io-channel-cells:
+  - input