How does AM1808 evm Boot ROM search for UBL?


I use AM1808 EVM.

From my study, I know the boot sequence is:

Boot ROM -> UBL on flash (spi) -> u-boot -> OS

My question is,

1. How  does the Boot ROM search for UBL on flash?

On AM1808 EVM, UBL is put at offset 0 on the spi flash.

Can we move UBL to other offset on the spi flash?

2. If we change the spi flash with one NAND flash in our design, where should we put UBL?