I have spoken with the developer of the rom of the xiaomi my pad, and he has answered me that it is not necessary to ortho bootloader, which uses the same as kitkat.
here your message:
That's not how it works. Bootloader has nothing to do with the Android version. The Mi Pad uses the stock 4.4 bootloader to boot all the OSes upto Oreo.
It is not enough that your device has a Tegra K1. There are many device specific changes in the kernel and userspace that would need accounting for. You could use our work and the Nvidia Shield Tablet's work as a reference, but a lot of work would need to be done from scratch. I recommend you do intense research if you plan on doing anything about it.