We have at least three questions (I wouldn't be surprised to find more if I went actively looking) where someone compiled their kernel and forgot a driver and so couldn't boot. These are candidates for merging. Alternatively, as none has a really good answer, create a master question, write a good answer and close the others as duplicates.
There's not much point in making a fourth question. I merged into Kernel can't find /dev/sda file during boot; all 6 answers make sense there. Good find