uboot: setup serial tty for qemu

features.in/uboot/config.mk

-use/uboot: use/kernel
+ifeq (,$(filter-out qcow2 qcow2c,$(IMAGE_TYPE)))
+ifeq (,$(filter-out aarch64 armh,$(ARCH)))
+UBOOT_TTY := use/tty/AMA0
+else
+UBOOT_TTY := /use/tty/S0
+endif
+endif
+
+use/uboot: use/kernel/initrd-setup $(UBOOT_TTY)
 	@$(call add_feature)
 	@$(call add,THE_LISTS,singleboard-tools)
+	@$(call try,TTY_DEV,tty1)
+	@$(call xport,TTY_DEV)

features.in/uboot/image-scripts.d/00-uboot-prepare

@@ -2,6 +2,12 @@
 
 [ "$GLOBAL_BASE_BOOTLOADER" = 'uboot' ] || exit 0
 
+if [ -n "$GLOBAL_TTY_RATE" ] ;then
+	TTY="$GLOBAL_TTY_DEV","$GLOBAL_TTY_RATE"
+else
+	TTY="$GLOBAL_TTY_DEV"
+fi
+
 # installkernel relies on existing extlinux.conf
 # with filled in `default' label
 mkdir -p /boot/extlinux
@@ -15,5 +21,5 @@ label linux
 	kernel /boot/vmlinuz
 	initrd /boot/initrd.img
 	fdtdir /boot/dtb
-	append root=LABEL=ROOT ro cma=192M console=tty1
+	append root=LABEL=ROOT ro cma=192M console=$TTY
 EOF