dt-bindings: display: ssd1307fb: Extend schema for SPI controllers

The Solomon SSD130x OLED displays can either have an I2C or SPI interface,
add to the schema the properties and examples for OLED devices under SPI.
Signed-off-by: NJavier Martinez Canillas <javierm@redhat.com>
Acked-by: NMark Brown <broonie@kernel.org>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NRob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220419214824.335075-3-javierm@redhat.com

Documentation/devicetree/bindings/display/solomon,ssd1307fb.yaml

@@ -38,9 +38,20 @@ properties:
   reset-gpios:
     maxItems: 1
 
+  # Only required for SPI
+  dc-gpios:
+    description:
+      GPIO connected to the controller's D/C# (Data/Command) pin,
+      that is needed for 4-wire SPI to tell the controller if the
+      data sent is for a command register or the display data RAM
+    maxItems: 1
+
   vbat-supply:
     description: The supply for VBAT
 
+  # Only required for SPI
+  spi-max-frequency: true
+
   solomon,height:
     $ref: /schemas/types.yaml#/definitions/uint32
     default: 16
@@ -220,14 +231,14 @@ examples:
             #address-cells = <1>;
             #size-cells = <0>;
 
-            ssd1307: oled@3c {
+            ssd1307_i2c: oled@3c {
                     compatible = "solomon,ssd1307";
                     reg = <0x3c>;
                     pwms = <&pwm 4 3000>;
                     reset-gpios = <&gpio2 7>;
             };
 
-            ssd1306: oled@3d {
+            ssd1306_i2c: oled@3d {
                     compatible = "solomon,ssd1306";
                     reg = <0x3c>;
                     pwms = <&pwm 4 3000>;
@@ -238,3 +249,30 @@ examples:
                     solomon,lookup-table = /bits/ 8 <0x3f 0x3f 0x3f 0x3f>;
             };
     };
+  - |
+    spi {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            ssd1307_spi: oled@0 {
+                    compatible = "solomon,ssd1307";
+                    reg = <0x0>;
+                    pwms = <&pwm 4 3000>;
+                    reset-gpios = <&gpio2 7>;
+                    dc-gpios = <&gpio2 8>;
+                    spi-max-frequency = <10000000>;
+            };
+
+            ssd1306_spi: oled@1 {
+                    compatible = "solomon,ssd1306";
+                    reg = <0x1>;
+                    pwms = <&pwm 4 3000>;
+                    reset-gpios = <&gpio2 7>;
+                    dc-gpios = <&gpio2 8>;
+                    spi-max-frequency = <10000000>;
+                    solomon,com-lrremap;
+                    solomon,com-invdir;
+                    solomon,com-offset = <32>;
+                    solomon,lookup-table = /bits/ 8 <0x3f 0x3f 0x3f 0x3f>;
+            };
+    };