The requirements for access to doctoral studies are set out in article 6 of Royal Decree 99/2011, of 28 January, which regulates official doctoral studies, as amended by Royal Decree 576/2023, of 4 July.
You can also consult these requirements on the website of the Doctoral School of the UVa:
https://esduva.uva.es/en/phd-students/access-admission-and-enrolment/access-requirements/