In case of PhD students of the Doctoral School the affiliation information related to the School also has to be added to publications according to the followings:
[Name of university], [Name of the school]
In the case of the School of Informatics:
Debreceni Egyetem, Informatikai Tudományok Doktori Iskola
Or in English:
University of Debrecen, Doctoral School of Informatics
If there is no way to mark more than one affiliation on the paper tha name of the School has to appear in footnote or in acknowledgement.