arm64: dts: renesas: Add Gray Hawk Single board support

Add initial support for the Renesas Gray Hawk Single board, which is
based on the R-Car V4M (R8A779H0) SoC:
  - Memory,
  - Crystal oscillators,
  - Serial console.

Based on the White Hawk Single DTS, and on a patch for the Gray Hawk
board stack in the BSP by Hai Pham.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/b657402113267acd57aece0b4c681b707e704455.1706194617.git.geert+renesas@glider.be

arch/arm64/boot/dts/renesas/Makefile

@@ -89,6 +89,8 @@ dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g0-white-hawk-ard-audio-da7212.dtb
 
 dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g2-white-hawk-single.dtb
 
+dtb-$(CONFIG_ARCH_R8A779H0) += r8a779h0-gray-hawk-single.dtb
+
 dtb-$(CONFIG_ARCH_R8A77951) += r8a779m1-salvator-xs.dtb
 r8a779m1-salvator-xs-panel-aa104xd12-dtbs := r8a779m1-salvator-xs.dtb salvator-panel-aa104xd12.dtbo
 dtb-$(CONFIG_ARCH_R8A77951) += r8a779m1-salvator-xs-panel-aa104xd12.dtb

arch/arm64/boot/dts/renesas/r8a779h0-gray-hawk-single.dts

+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/*
+ * Device Tree Source for the R-Car V4M Gray Hawk Single board
+ *
+ * Copyright (C) 2023 Renesas Electronics Corp.
+ * Copyright (C) 2024 Glider bv
+ */
+
+/dts-v1/;
+#include "r8a779h0.dtsi"
+
+/ {
+	model = "Renesas Gray Hawk Single board based on r8a779h0";
+	compatible = "renesas,gray-hawk-single", "renesas,r8a779h0";
+
+	aliases {
+		serial0 = &hscif0;
+	};
+
+	chosen {
+		bootargs = "ignore_loglevel";
+		stdout-path = "serial0:921600n8";
+	};
+
+	memory@48000000 {
+		device_type = "memory";
+		/* first 128MB is reserved for secure area. */
+		reg = <0x0 0x48000000 0x0 0x78000000>;
+	};
+
+	memory@480000000 {
+		device_type = "memory";
+		reg = <0x4 0x80000000 0x1 0x80000000>;
+	};
+};
+
+&extal_clk {
+	clock-frequency = <16666666>;
+};
+
+&extalr_clk {
+	clock-frequency = <32768>;
+};
+
+&hscif0 {
+	uart-has-rtscts;
+	status = "okay";
+};
+
+&scif_clk {
+	clock-frequency = <24000000>;
+};