I'm interested to know what happens when users with a quad board don't change the dtb name and boot using the dual dtb? (or should the defaults be switched to quad?). Also, looking at the device-tree files in the kernel, didn't we (you) also used to ship an image for the Hummingboard devices?
Users don't need to set any dtb name because all magic is happening automatically in u-boot. U-boot for solidrun check the SoC type and sets one part of the dtb (imx6dl or imx6q). Then it also checks the SoM type (cubox, hummingboard, hummingboard2) and at the end also SoM revision (v15 or nothing). So same image runs on every device from solidrun without knowing what type it is and without setting dtb name. Same thing is happening on u-boot for Wandboard and Udoo. But there is probably just setting SoC type (at least this was true for Udoo when I add support for it).
But maybe mainline u-boot remove or broke all those things 
So lrusak: you still think it doesn't matter how u-boot works? 