The most important thing to do is to select one of the newer BSP .cap files and burn it to the flash chip on board.
The out-of-the-box version doesn't support SD card booting what so ever, so that's the first thing to do.
Since you don't give any context, I think this is the best advice I can give you right now.
And please try to read through the link given by mon2 as well. Lots of pointers in there also.
As you said I already have the latest firmware for the board.
I've taken a look at the link that mon2 gave me but nothing of that work for me.
The thing is that I can boot from the SD card the debian image, but I have to do it manually (as the author of the image explain here). What i'm trying to get is that, as soon as I power up the board it should boot from the SDcard wihout going first to the SPI flash, just boot the debian image. (similar like saying in a PC to boot from the usb instead of booting from the HDD). I like to know if it possible to do that or not.
I'm pretty sure the boot stuff is hard-coded into the the BIOS.
I think the best venue is to figure out what boot options are needed and then generate a new .cap
file with those options as a new entry in the grub/menu.lst file.
You can use the E button to tweak the boot line until it works.
I do not at present believe that you can bypass the SPI grub.
Better to work with it than trying to get around it.
It's theoretically not needed to recreate the SPI iname if you just want to boot from something else. Grub in the SPI is set to check for a boot/grub/grub.conf on a first active partition on the SD card or a USB thumbdrive connected to Galileo. So you should be able to automate booting into Debian by just placing the grub config properly.
Now I'm using "theoretically" above, which means that it may be the case that Galileo's grub won't be able to boot the Debian kernel - it's a bit old and modified version from Yocto and there were reports of unsuccessful attempts to make it boot other kernels (though that wasn't Debian but rather some more exotic things). If that's the case, then rebuilding SPI won't help anyway, unless you relace grub there (and that's a project in itself, I'd say).
So my suggestion would be to try that boot/grub/grub.conf way and see if it works - it may be a very easy answer (or a checked possibility :-) )