Start to get layers + keymaps pulled in from DTS.

dts/bindings/zmk,keymap.yaml

@@ -0,0 +1,13 @@
+description: |
+  Allows defining a keymap composed of multiple layers
+
+compatible: "zmk,keymap"
+
+properties:
+  label:
+    type: string
+    required: true
+
+  layers:
+    type: phandles
+    required: true

dts/bindings/zmk,layers.yaml

@@ -0,0 +1,14 @@
+description: |
+  Allows defining the various keymap layers for use.
+
+compatible: "zmk,layers"
+
+child-binding:
+  description: "A layer to be used in a keymap"
+
+  properties:
+    label:
+      type: string
+    keys:
+      type: array
+