The /opt/freecalypso host directory tree used by the present FC host tools
package and by various add-ons to it does NOT follow the traditional Unix/Linux
file system hierarchy standard (FHS), instead it is a highly specialized
directory tree that is meant to be private to FreeCalypso, with its structure
defined solely by the Mother and no one else.  The following subdirectories are
currently defined:

aud-*: these directories appear if you install our optional
fc-audio-config package, and contain subtrees to be uploaded by
production line scripts into target device FFS under /aud via fc-fsio.

batteries and charging: these subtrees come from fc-battery-conf
(optional just like fc-audio-config) and are meant to be used with
fc-fsio write-battery-table and write-charging-config commands.

bin and include are the only subdirectories under /opt/freecalypso
which follow traditional UNIX directory layout; include was added so
that packages external to the core FC host tools package like
fc-rfcal-tools and freecalypso-ui-dev can use rvinterf headers.

gcc: the recommend install location for our ARM7 gcc toolchain is
/opt/freecalypso/gcc.

helpfiles subdir contains help files for those FC host utilities which
implement a help command.

loadtools subdir contains hardware parameter files and init scripts
which underlie the all-important -h option to fc-loadtool, fc-iram and
fc-xram, collectively known as loadtools.

rfcal subdir only appears if you are doing RF calibration and install
fc-rfcal-tools, and some of the necessary config files under that
subdir you have to create yourself using your own RF knowledge specific
to your particular setup.

target-bin contains ARM7 target binaries used under the hood by
loadtools.

The basic minimal form of the /opt/freecalypso tree is populated when
you install FC host tools, but it is further enriched if and when you
install further add-ons (fc-audio-config, fc-battery-conf,
fc-rfcal-tools) which are more specialized and not required for all
users.  I expect to have more additions in the future: for example,
when we start using the Melody E1 mechanism in our planned FC Libre
Dumbphone, there will be a FreeCalypso ringtones package that will
install E1-format melody files somewhere under /opt/freecalyso, to be
subsequently uploaded into the actual phones via fc-fsio, initially at
production time and optionally by end users.