bootdev undefined

I modify my mtd flash partitions in flash based on information that I
read from a special sector in flash. The problem is that, then, I don't
know where the rootfs will be housed in. It could be in /dev/mtdblock2
or /dev/mtdblock3. Could I instruct the mtd subsystem to create a
special device beside the normal mtdblockn devices based on the info in
the partition table?
=20
Thank you in advance!=20