Installing Slackware 14.2 on Toshiba ac 100 with mainline kernel

The tasks:

• - switch to GPT partitioning and partition the EMMC
• - compile kernel, make it bootable
• - take slackware root

Before starting, keep at mind that internal EMMC is reffered as /dev/mmcblk0p, but if you plug SD card before loading... well, too early, it will became /dev/mmcblk0p, not 1p, as you can expect. This makes AC100 to boot at least root fs from SD card.
First, follow ARCH linux installation guide. The easiest way to compile kernel is to do it on some other ARM computer - saying, on Orange PI (Banana or Raspberry, if you prefer). Stop following this guide until you have only /boot (and /lib with kernel modules, and /etc/ with fstab) on your's EMMC card.
Then take Slackware arm root from here and copy it to EMMC (without boot and preserving /etc/fstab and /lib/kernel modules). Check twice you have a correct fstab (first, root fs and after you boot it - tmpfs and udev)
Next, take a full slackware-arm to sd card, boot the system, plug sd card, mount it, check you have udev running and.. you know what to do with slackware.