The BBC series Bodyguard was nominated for two Golden Globes awards: Best Television Series - Drama and Best Actor - Television Series Drama. It is a self contained story of six episodes, fewer than several of the series which were nominated for miniseries awards. Why was it nominated for regular series awards rather than miniseries awards? And are there restrictions on qualifications for these categories, or do the producers of these shows choose what to submit nominations for?
The studio or publicist chooses which category to submit their show, which, although it can be overridden by the HPFA membership (by 2/3 vote), usually stands. So it's basically up to them.
There is actually nothing in the official rules saying that a series has to be multi-year, whereas the limited series rules explicitly say "Must tell a complete, non-recurring story." Golden Globes PDF
(As an aside, there was actually a small controversy last year, when Big Little Lies was entered as a limited series, even though it had already been renewed for a new year. A new rule was added for 2019 saying "A television limited series that is later renewed for an additional season shall be classified as a series or again as a limited series in that later season depending on the degree of continuity in theme, storyline, main characters and production supervision from the original limited series to the later year of the series." Variety)