buildroot/board/olimex/a20_olinuxino/rootfs_overlay/boot/extlinux/extlinux.conf

label Olinuxino
    kernel /boot/zImage
    fdtdir /boot
    append console=ttyS0,115200 root=/dev/mmcblk0p1 rootwait panic=10 drm_kms_helper.drm_leak_fbdev_smem=1 drm_kms_helper.drm_fbdev_overalloc=200 ${extra}