In short, the legacy u-boot and kernel (3.10.x) from the BSP boot differently compared to upstream mainline u-boot and kernel. BSP uses a binary blob (boot0) to initialize DRAM and then u-boot in 32bit mode, mainline uses an open u-boot spl loader and u-boot in 64bit mode which also changes how the kernel is entered.
Come have a chat in the Pine IRC channel >>