"yasokada via Lists.Zephyrproject.Org"
[Edited Message Follows]I checked the bossac source code and the option seems to be available,
so it doesn't look like there's a problem with the bossac.py code in the
zephyr repository that is using --offset:
I'm not sure why the bossac that ships with the Zephyr SDK doesn't have
the --offset option. I checked the version that ships with bossa-cli on
Ubuntu 18.04 and it doesn't seem to have it either, as you say.
I would try compiling bossac from source trying that version. Please
consider filing a bug against the Zephyr SDK about the missing option if
that solves your issue.
By the way, it looks like the person who added this board in commit
4f9864b15b263dcf7d6e204ac79f3d96a8a30e64 is no longer active on Zephyr
(the last contribution they made is from March 2018), so it's possible
that this board is unmaintained.
Hope you figure out your issue.