I don't know about referencing the NAND as one device, but these are the notes I have made (copied from an earlier thread here, most likely)
mount -t jffs2 /dev/mtdblock2 /mnt/block2 -o ro
dev: size erasesize name
mtd0: 00100000 00020000 "u-boot"
mtd1: 00400000 00020000 "uImage"
mtd2: 1fb00000 00020000 "root"
ubiattach /dev/ubi_ctrl -m 2 -d 0
mount -t ubifs ubi0_0 /mnt/nand
mount -t ubifs ubi0:rootfs /mnt/nand
(I'm not quite sure why I have the umount options listed, like I say, it was probably copied from somewhere else).