arm: qemu: Add a devicetree file for qemu_arm

This uses QEMU virt which creates its own devicetree.

Add an empty version of this file, so that we can at least build this
board when devicetrees are required.

Tested-by: Heinrich Schuchardt <heinrich.schuchardt@canaonical.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 7f622fe..eaad3b6 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1162,6 +1162,8 @@
 
 dtb-$(CONFIG_TARGET_EA_LPC3250DEVKITV2) += lpc3250-ea3250.dtb
 
+dtb-$(CONFIG_ARCH_QEMU) += qemu-arm.dtb
+
 targets += $(dtb-y)
 
 # Add any required device tree compiler flags here
diff --git a/arch/arm/dts/qemu-arm.dts b/arch/arm/dts/qemu-arm.dts
new file mode 100644
index 0000000..230c630
--- /dev/null
+++ b/arch/arm/dts/qemu-arm.dts
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * Empty device tree for qemu_arm
+
+ * Copyright 2021 Google LLC
+ */
+
+/dts-v1/;
+
+/ {
+};
diff --git a/configs/qemu_arm_defconfig b/configs/qemu_arm_defconfig
index 8ce5540..6bec0ae 100644
--- a/configs/qemu_arm_defconfig
+++ b/configs/qemu_arm_defconfig
@@ -5,6 +5,7 @@
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x40000
 CONFIG_ENV_SECT_SIZE=0x40000
+CONFIG_DEFAULT_DEVICE_TREE="qemu-arm"
 CONFIG_TARGET_QEMU_ARM_32BIT=y
 CONFIG_DEBUG_UART_BASE=0x9000000
 CONFIG_DEBUG_UART_CLOCK=0