Acordding to this a SDIO stack is allready available for linux.
I'm sure if it were that simple people would have ported it to the collies/poodles...
But AFAIK they run undocumented SD chips, which are only able to work with Sharp's SD/MMC driver which is largely why collies/poodles are stuck at the 2.4.18 kernel.
It's a shame, but Sharp will not or cannot release the necessary specs or source code.