arm64: dts: add support for A9 based Amlogic BY401

Add basic support for the A9 based Amlogic BY401 board, which describes
the following components: CPU, GIC, IRQ, Timer and UART.
These are capable of booting up into the serial console.

Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://patch.msgid.link/20260423-a9-baisc-dts-v4-2-c26b480a068c@amlogic.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/arm64/boot/dts/amlogic/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 dtb-$(CONFIG_ARCH_MESON) += amlogic-a4-a113l2-ba400.dtb
 dtb-$(CONFIG_ARCH_MESON) += amlogic-a5-a113x2-av400.dtb
+dtb-$(CONFIG_ARCH_MESON) += amlogic-a9-a311y3-by401.dtb
 dtb-$(CONFIG_ARCH_MESON) += amlogic-c3-c302x-aw409.dtb
 dtb-$(CONFIG_ARCH_MESON) += amlogic-c3-c308l-aw419.dtb
 dtb-$(CONFIG_ARCH_MESON) += amlogic-s6-s905x5-bl209.dtb

arch/arm64/boot/dts/amlogic/amlogic-a9-a311y3-by401.dts

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright (c) 2026 Amlogic, Inc. All rights reserved.
+ */
+
+/dts-v1/;
+
+#include "amlogic-a9.dtsi"
+/ {
+	model = "Amlogic A311DY3 BY401 Development Board";
+	compatible = "amlogic,by401", "amlogic,a9";
+	#address-cells = <2>;
+	#size-cells = <2>;
+
+	aliases {
+		serial0 = &uart_b;
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x0 0x0 0x0 0x80000000>;
+	};
+
+	reserved-memory {
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		/* 35 MiB reserved for ARM Trusted Firmware */
+		secmon_reserved: secmon@5000000 {
+			compatible = "shared-dma-pool";
+			reg = <0x0 0x05000000 0x0 0x2300000>;
+			no-map;
+		};
+	};
+};
+
+&uart_b {
+	status = "okay";
+};

arch/arm64/boot/dts/amlogic/amlogic-a9.dtsi

@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright (c) 2026 Amlogic, Inc. All rights reserved.
+ */
+
+#include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/interrupt-controller/arm-gic.h>
+#include <dt-bindings/gpio/gpio.h>
+
+/ {
+	interrupt-parent = <&gic>;
+
+	cpus {
+		#address-cells = <2>;
+		#size-cells = <0>;
+
+		cpu0: cpu@0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x0>;
+			enable-method = "psci";
+		};
+
+		cpu1: cpu@100 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x100>;
+			enable-method = "psci";
+		};
+
+		cpu2: cpu@200 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x200>;
+			enable-method = "psci";
+		};
+
+		cpu3: cpu@300 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x300>;
+			enable-method = "psci";
+		};
+
+		cpu4: cpu@400 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x400>;
+			enable-method = "psci";
+		};
+
+		cpu5: cpu@500 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a55";
+			reg = <0x0 0x500>;
+			enable-method = "psci";
+		};
+
+		cpu6: cpu@600 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a78";
+			reg = <0x0 0x600>;
+			enable-method = "psci";
+		};
+
+		cpu7: cpu@700 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a78";
+			reg = <0x0 0x700>;
+			enable-method = "psci";
+		};
+	};
+
+	timer {
+		compatible = "arm,armv8-timer";
+		interrupts = <GIC_PPI 13 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_PPI 14 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_PPI 11 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_PPI 10 IRQ_TYPE_LEVEL_LOW>;
+	};
+
+	psci {
+		compatible = "arm,psci-1.0";
+		method = "smc";
+	};
+
+	xtal: xtal-clk {
+		compatible = "fixed-clock";
+		clock-frequency = <24000000>;
+		clock-output-names = "xtal";
+		#clock-cells = <0>;
+	};
+
+	soc {
+		compatible = "simple-bus";
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		gic: interrupt-controller@ff800000 {
+			compatible = "arm,gic-v3";
+			#interrupt-cells = <3>;
+			#address-cells = <0>;
+			interrupt-controller;
+			reg = <0x0 0xff800000 0 0x10000>,
+			      <0x0 0xff840000 0 0x100000>;
+			interrupts = <GIC_PPI 9 0xf04>;
+		};
+
+		aobus: bus@ffa00000 {
+			compatible = "simple-bus";
+			reg = <0x0 0xffa00000 0x0 0x100000>;
+			#address-cells = <2>;
+			#size-cells = <2>;
+			ranges = <0x0 0x0 0x0 0xffa00000 0x0 0x100000>;
+
+			uart_b: serial@1e000 {
+				compatible = "amlogic,a9-uart",
+					     "amlogic,meson-s4-uart";
+				reg = <0x0 0x1e000 0x0 0x18>;
+				interrupts = <GIC_SPI 66 IRQ_TYPE_EDGE_RISING>;
+				clocks = <&xtal>, <&xtal>, <&xtal>;
+				clock-names = "xtal", "pclk", "baud";
+				status = "disabled";
+			};
+		};
+	};
+};