I recommend to use NXP's BSP intended for the ls1043ARDB and develop some modifications on it, due the BSP layer adds support for a particular hardware device or family of devices to Yocto. This support usually includes the bootloader, device tree blobs, and additional kernel drivers needed to boot Linux on that specific hardware.
For a better understanding of it I suggest to read the chapter 7 in the book (all the book could be a good idea)
Vasquez, Frank; Simmonds, Chris. Mastering Embedded Linux Programming: Create fast and reliable embedded solutions with Linux 5.4 and the Yocto Project 3.1 (Dunfell), 3rd Edition Packt Publishing.
We don't have one guide for the whole process you need to do in order to have the right image for your development, we have guides for particular situations.