dt-bindings: input: touchscreen: st1232: add touch-overlay example

The touch-overlay feature adds support for segments (touch areas) on the
touchscreen surface that represent overlays with clipped touchscreen
areas and printed buttons.

Add nodes for a clipped touchscreen and overlay buttons to the existing
example.

Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Javier Carrasco <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/touchscreen/sitronix,st1232.yaml

···
 
 examples:
   - |
+    #include <dt-bindings/input/linux-event-codes.h>
     i2c {
             #address-cells = <1>;
             #size-cells = <0>;
···
                     reg = <0x55>;
                     interrupts = <2 0>;
                     gpios = <&gpio1 166 0>;
+
+                    touch-overlay {
+                            segment-0 {
+                                    label = "Touchscreen";
+                                    x-origin = <0>;
+                                    x-size = <240>;
+                                    y-origin = <40>;
+                                    y-size = <280>;
+                            };
+
+                            segment-1a {
+                                    label = "Camera light";
+                                    linux,code = <KEY_LIGHTS_TOGGLE>;
+                                    x-origin = <40>;
+                                    x-size = <40>;
+                                    y-origin = <0>;
+                                    y-size = <40>;
+                            };
+
+                            segment-2a {
+                                    label = "Power";
+                                    linux,code = <KEY_POWER>;
+                                    x-origin = <160>;
+                                    x-size = <40>;
+                                    y-origin = <0>;
+                                    y-size = <40>;
+                            };
+                    };
             };
     };