Package: flash-kernel Severity: normal syslinux-style /boot/extlinux/extlinux.conf superseed boot.scr in recent u-boot versions and seems to be the way forward for u-boot configuration, but I couldn't find anything to automatically generate them in Debian.
Long story short, I manually installed Debian Jessie (as well as linux-image-4.0.0-2-armmp and u-boot from u-boot-sunxi=2015.04+dfsg1-2) on an A20-OLinuXino-LIME2 from Olimex but couldn't get it to boot (even with the boot.scr created by flash-kernel when invoked in a chroot with “FK_MACHINE="Olimex A20-OLinuXino-LIME2" flash-kernel”) until I created the simple /boot/extlinux/extlinux.conf file attached. I'm not sure whether flash-kernel is the correct package to implement this feature, but there should be a way to automaticaly generate such files.
menu title LIME2 boot menu timeout 10 ontimeout linux LABEL linux KERNEL /boot/vmlinuz-4.0.0-2-armmp INITRD /boot/initrd.img-4.0.0-2-armmp fdt /boot/dtb-4.0.0-2-armmp append root=/dev/mmcblk0p1 ro rootwait