arm: bcmbca: add bcm6856 SoC support under CONFIG_ARCH_BCMBCA

BCM6856 is a Broadcom B53 based PON Gateway SoC. It is part of the BCA
(Broadband Carrier Access origin) chipset family. Like other Broadband
SoC, this patch adds it under CONFIG_BCM6856 chip config and
CONFIG_ARCH_BCMBCA platform config.

This initial support includes a bare-bone implementation and dts with
CPU subsystem, memory and Broadcom uart. This SoC is supported in the
linux-next git repository so the dts and dtsi files are copied from
linux.

The u-boot image can be loaded from flash or network to the entry point
address in the memory and boot from there to the console.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>
diff --git a/arch/arm/dts/bcm6856.dtsi b/arch/arm/dts/bcm6856.dtsi
new file mode 100644
index 0000000..0bce649
--- /dev/null
+++ b/arch/arm/dts/bcm6856.dtsi
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright 2022 Broadcom Ltd.
+ */
+
+#include <dt-bindings/interrupt-controller/irq.h>
+#include <dt-bindings/interrupt-controller/arm-gic.h>
+
+/ {
+	compatible = "brcm,bcm6856", "brcm,bcmbca";
+	#address-cells = <2>;
+	#size-cells = <2>;
+
+	interrupt-parent = <&gic>;
+
+	cpus {
+		#address-cells = <2>;
+		#size-cells = <0>;
+
+		B53_0: cpu@0 {
+			compatible = "brcm,brahma-b53";
+			device_type = "cpu";
+			reg = <0x0 0x0>;
+			next-level-cache = <&L2_0>;
+			enable-method = "psci";
+		};
+
+		B53_1: cpu@1 {
+			compatible = "brcm,brahma-b53";
+			device_type = "cpu";
+			reg = <0x0 0x1>;
+			next-level-cache = <&L2_0>;
+			enable-method = "psci";
+		};
+
+		L2_0: l2-cache0 {
+			compatible = "cache";
+		};
+	};
+
+	timer {
+		compatible = "arm,armv8-timer";
+		interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
+			<GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
+			<GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
+			<GIC_PPI 10 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>;
+	};
+
+	pmu: pmu {
+		compatible = "arm,cortex-a53-pmu";
+		interrupts = <GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>,
+			<GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>;
+		interrupt-affinity = <&B53_0>, <&B53_1>;
+	};
+
+	clocks: clocks {
+		periph_clk:periph-clk {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <200000000>;
+		};
+	};
+
+	psci {
+		compatible = "arm,psci-0.2";
+		method = "smc";
+	};
+
+	axi@81000000 {
+		compatible = "simple-bus";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges = <0x0 0x0 0x81000000 0x8000>;
+
+		gic: interrupt-controller@1000 {
+			compatible = "arm,gic-400";
+			#interrupt-cells = <3>;
+			interrupt-controller;
+			reg = <0x1000 0x1000>, /* GICD */
+				<0x2000 0x2000>, /* GICC */
+				<0x4000 0x2000>, /* GICH */
+				<0x6000 0x2000>; /* GICV */
+			interrupts = <GIC_PPI 9 (GIC_CPU_MASK_SIMPLE(2) |
+					IRQ_TYPE_LEVEL_HIGH)>;
+		};
+	};
+
+	bus@ff800000 {
+		compatible = "simple-bus";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges = <0x0 0x0 0xff800000 0x800000>;
+
+		uart0: serial@640 {
+			compatible = "brcm,bcm6345-uart";
+			reg = <0x640 0x18>;
+			interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&periph_clk>;
+			clock-names = "refclk";
+			status = "disabled";
+		};
+	};
+};