arm: dts: Create common rz-g2-beacon-u-boot file

The rzg2_beacon_defconfig creates an image for RZ/G2[MNH] and
as such creates three different device trees and each of them
have a corresponding -u-boot.dtsi file which are basically
copies of each other.  Create a common include file to be
referenced by each of the respective board-u-boot.dtsi files
to reduce duplicate code and simplify support going forward.
This also restores some lost functionality from the device
tree re-sync and updates the MAINTAINER file to include all
beacon-renesom device tree files.

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/arch/arm/dts/rz-g2-beacon-u-boot.dtsi b/arch/arm/dts/rz-g2-beacon-u-boot.dtsi
new file mode 100644
index 0000000..ef0b96a
--- /dev/null
+++ b/arch/arm/dts/rz-g2-beacon-u-boot.dtsi
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2021 LogicPD dba Beacon EmbeddedWorks
+ */
+
+/ {
+	aliases {
+		spi0 = &rpc;
+	};
+
+	soc {
+		u-boot,dm-pre-reloc;
+	};
+};
+
+&cpg {
+	u-boot,dm-pre-reloc;
+};
+
+&ehci0 {
+	clocks = <&cpg CPG_MOD 703>, <&cpg CPG_MOD 704>, <&versaclock5 3>;
+};
+
+&ehci1 {
+	clocks = <&cpg CPG_MOD 703>, <&cpg CPG_MOD 704>, <&versaclock5 3>;
+};
+
+&extal_clk {
+	u-boot,dm-pre-reloc;
+};
+
+&extalr_clk {
+	u-boot,dm-pre-reloc;
+};
+
+&prr {
+	u-boot,dm-pre-reloc;
+};
+
+&rpc {
+	compatible = "renesas,rcar-gen3-rpc";
+	num-cs = <1>;
+	spi-max-frequency = <40000000>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+	status = "okay";
+
+	flash0: spi-flash@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		reg = <0>;
+		compatible = "spi-flash", "jedec,spi-nor";
+		spi-max-frequency = <40000000>;
+		spi-tx-bus-width = <1>;
+		spi-rx-bus-width = <1>;
+	};
+};
+
+&sdhi0 {
+	/delete-property/ cd-gpios;
+	sd-uhs-sdr12;
+	sd-uhs-sdr25;
+	sd-uhs-sdr104;
+	max-frequency = <208000000>;
+};
+
+&sdhi2 {
+	status = "disabled";
+};
+
+&sdhi3 {
+	mmc-ddr-1_8v;
+	mmc-hs200-1_8v;
+	mmc-hs400-1_8v;
+};