add position maps

app/boards/shields/boardsource3x4/boardsource3x4-layouts.dtsi

@@ -46,4 +46,25 @@
             , <&key_physical_attrs 100 100    200 300    0 0 0>
             ;
     };
+
+    position_map {
+        compatible = "zmk,physical-layout-position-map";
+
+        horizontal_map: horizontal {
+            // A  7  8  9
+            // B  4  5  6
+            // C  1  2  3
+            physical-layout = <&horizontal_physical_layout>;
+            positions = </* 0 */ 1 2 3 4 5 6 7 8 /* 9 10 11 */>;
+        };
+        vertical_map: verctical {
+            // A  B  C
+            // 7  8  9
+            // 4  5  6
+            // 1  2  3
+            physical-layout = <&vertical_physical_layout>;
+            positions = </* 0 */ 3 4 5 1 6 7 8 2 /* 9 10 11 */>;
+        };
+    };
+
 };