Add RoMac plus v4 support on nice nano v1

app/boards/shields/romac_plus/romac_plus.dtsi

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2020 Pete Johanson
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <dt-bindings/zmk/matrix-transform.h>
+
+/ {
+	chosen {
+		zmk,kscan = &kscan0;
+		zmk,matrix_transform = &default_transform;
+	};
+
+	default_transform: keymap_transform_0 {
+		compatible = "zmk,matrix-transform";
+		columns = <3>;
+		rows = <4>;
+
+		map = <
+RC(0,0) RC(0,1) RC(0,2)
+RC(1,0) RC(1,1) RC(1,2)
+RC(2,0) RC(2,1) RC(2,2)
+RC(3,0) RC(3,1) RC(3,2)
+		>;
+	};
+
+	kscan0: kscan {
+		compatible = "zmk,kscan-gpio-matrix";
+		label = "KSCAN";
+
+		diode-direction = "col2row";
+		row-gpios
+			= <&pro_micro_d 5 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+			, <&pro_micro_d 4 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+			, <&pro_micro_d 0 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+			, <&pro_micro_d 1 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+			;
+		
+	};
+
+	left_encoder: encoder_left {
+		compatible = "alps,ec11";
+		label = "LEFT_ENCODER";
+		a-gpios = <&pro_micro_d 16 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
+		b-gpios = <&pro_micro_d 14 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
+		resolution = <4>;
+		status = "disabled";
+	};
+
+	sensors {
+		compatible = "zmk,keymap-sensors";
+		sensors = <&left_encoder>;
+	};
+	
+	bt_unpair_combo: bt_unpair_combo {
+		compatible = "zmk,bt-unpair-combo";
+	};
+
+	// TODO: per-key RGB node(s)?
+};