In message E1DW7ze-0001qs-BS@sc8-sf-mx2.sourceforge.net you wrote:

I'm quite new to U-Boot. I'm focus on such a board:

CPU: Intel XScale GDPXA255A0C400 Flash: Intel StrataFlash 16MB x 2 SDRAM: Samsung K4S5616320 32MB x 2

This is not a board. This is just a description of some components. I guess there is a vendor and a product name for your board?

I'm confused with the board names within the folder "/board". Which board shall I begin with?

Have a look at the Makefile which other Xscale systems are supported, check which chips these use (search the source files, search the data sheets, etc.), then chose one.

Best regards,

Wolfgang Denk