Verify BSP settings

Got that one resolved!
I decided to re-build bootloader and tried to follow the GSRD v14.0 - Generating and Compiling the Preloader
When I copied the binary to my uSD card the system didn't boot - likely some of the important details like partition type etc. I went back to my previous scripts that use mainline u-boot (branch v2019.07).
After some searching how the BSP specific information gets included into the u-boot-with-spl_DE0.sfp u-boot binary I discovered in the u-boot build tree the file

board/terasic/de0-nano-soc/qts/pinmux_config.h

I edited desired "...USEFPGA" values to "1"

    abbreviated ...
        1, /* UART1USEFPGA */
	0, /* CAN1USEFPGA */
	0, /* USB1USEFPGA */
	0, /* I2C3USEFPGA */
	1, /* I2C2USEFPGA */
...

rebuilt the u-boot, placed on my uSD card and the previously failing kernel with corresponding drivers and device tree started to work as expected.
Hoping this may help someone else.
Martin