Jetson TK1 SPI Boot Query

we are trying to boot Jetson TK1 from SPI. We have done some research related to it and get to a point that you don’t have software support to flash the SPI using your NVFlash tool.
But if we find the way to flash it externally then what can be the procedure? Can we get any information that at what addresses of SPI Flash we have to write our BCT and Uboot?
One more question that we have is, when we turn on the Jetson TK 1, it’s BOOT ROM code copies the uboot from eMMC to RAM when bootstrap settings are for eMMC. if we do the bootstraps settings for SPI Boot then do BOOT ROM code have drivers to communicate with SPI flash and copy uboot from it to RAM?

There are several topics for your reference: