I've build a new file system with Builtroot. I then copied all of the files onto a second partition of the SD card. Now I want to boot Linux and use the non-volatile file system on mmcblk0p2. I modified the DTS file to set root=/dev/mmcblk0p2. But when Linux boots it still uses the initramfs file system. How can I get the kernel to use and mount the other file system?