[coreboot] Rebuilding coreboot image generation

[Julius Werner]

> What I'd like to see come out of this is a dts-like set of flash
> descriptors, with the rules left in the makefiles. At the very least,
> dts is not a new language.

Just wanted to point out (without trying to usurp any of the ongoing
discussion in that doc) that we already have an FMAP descriptor
language that was implemented in cbfstool half a year ago, because I
don't think that got much visibility upstream when it was merged.
That's the FMD (flash map descriptor) format some of us are talking
about in those comments, which was developed in anticipation of a
build system redesign like this. It's aiming to describe FMAPs in a
clean, flexible way without the cruft of a format (dts) that was never
really meant for that purpose, and has some nice features (like
variable-sized sections) built-in. The parser can be seen in
util/cbfstool/fmd.c, and a sample file would look something like this
(in general, '@offset' is the base offset to the parent section and
the number after the space is the size):

HOST_FIRMWARE at 0xff800000 8M {
        SI_ALL 2M {
                SI_DESC 4K
                SI_ME 0x1ff000
        }
        SI_BIOS {
                RW_A 0xf0000 {
                        VBLOCK_A 64K
                        RW_MAIN_A
                        RW_FWID_A 0x40
                }
                RW_B 0xf0000 {
                        VBLOCK_B 64K
                        RW_MAIN_B
                        RW_FWID_B 0x40
                }
                RO at 4M {
                        RO_VPD 16K
                        FMAP at 0x10000 2K
                        RO_FRID 0x40
                        GBB at 0x11000
                        RO_MAIN 1M
                }
        }
}