I have a iMX8mp board. I created a yocto image and works just fine. It creates 2 partitions bootfs and rootfs. I want to create a 3rd partition rootfs2. Clone rootfs partition to rootfs2 into the device in the extra space. And boot from there. This is to do over the air updates. When an update fails to boot then just switch and boot from the original one.
On as raspberry pi is actually very simple. You just open the cmdline.txt file on the boot partition. Modify the root=PARTUUID=XXXXXX-XX to the values you want.
The iMX8mp board uses uboot. Seems that it is possible to modify it to achieve this. However I was not able to find much documentation on how to do this.
