[Yaffs] Query - Interface between YAFF and SD card ?

Hello everybody,

I am new to this group and have just start to look the yaff code and docs, I
have some of the basic doubts about the whole system on which Linux YAFF
running.

As last week Google phone has been launched with lot of fanfare, it has
linux as it's OS, my doubt is if my phone is supporting the SD card (which
it of course does) then how the linux able to read/write to the SD card as
generally SD card have been formatted in the FAT filesystem (my assumption
in thinking that most of the users would transfer the media files from their
to the windows PC's).

What is the interface in between the YAFF file system and the SD driver
through which file system is able to detect the SD card and do corresponding
operation of read/write?

Sorry for asking this basic question but just due to curiosity I am asking
this.

Thanks,
Gaur