So here the 'serial' is declared as mandatory. It's optional in the XML
parser/formatter and mandatory in the commandline formatter. With other
devices it's optional so it's most likely going to need an <optional>
block.
This series is also completely lacking documentation
(docs/formatdomain.rst) documenting bot the new controller and disk
type.
As described earlier, the intention is for the serial field to be mandatory.
Perhaps the parser/formatter handling led to some confusion? Any suggestions are very
welcome.
I'll add documentation for it in docs/formatdomain.rst.