ARM: dts: Add Raspberry Pi 400 support

The Raspberry Pi 400 is like a Pi 4 B designed into a keyboard. But there
are some minor differences:

- higher CPU clock rate (1.8 GHz)
- different Wifi chip (BCM43456)
- power off is now handled via GPIO
- no ACT LED
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/1622981777-5023-7-git-send-email-stefan.wahren@i2se.comSigned-off-by: Nicolas Saenz Julienne <nsaenz@kernel.org>

arch/arm/boot/dts/Makefile

@@ -88,6 +88,7 @@ dtb-$(CONFIG_ARCH_BCM2835) += \
 	bcm2837-rpi-3-b.dtb \
 	bcm2837-rpi-3-b-plus.dtb \
 	bcm2837-rpi-cm3-io3.dtb \
+	bcm2711-rpi-400.dtb \
 	bcm2711-rpi-4-b.dtb \
 	bcm2835-rpi-zero.dtb \
 	bcm2835-rpi-zero-w.dtb

arch/arm/boot/dts/bcm2711-rpi-400.dts

+// SPDX-License-Identifier: GPL-2.0
+/dts-v1/;
+#include "bcm2711-rpi-4-b.dts"
+
+/ {
+	compatible = "raspberrypi,400", "brcm,bcm2711";
+	model = "Raspberry Pi 400";
+
+	chosen {
+		/* 8250 auxiliary UART instead of pl011 */
+		stdout-path = "serial1:115200n8";
+	};
+
+	leds {
+		/delete-node/ led-act;
+
+		led-pwr {
+			gpios = <&gpio 42 GPIO_ACTIVE_HIGH>;
+		};
+	};
+
+	gpio-poweroff {
+		compatible = "gpio-poweroff";
+		gpios = <&expgpio 5 GPIO_ACTIVE_HIGH>;
+	};
+};
+
+&expgpio {
+	gpio-line-names = "BT_ON",
+			  "WL_ON",
+			  "",
+			  "GLOBAL_RESET",
+			  "VDD_SD_IO_SEL",
+			  "CAM_GPIO",
+			  "SD_PWR_ON",
+			  "SD_OC_N";
+};
+
+&genet_mdio {
+	clock-frequency = <1950000>;
+};
+
+&pm {
+	/delete-property/ system-power-controller;
+};