There's a specific page on Wikipedia about Mitochondrial DNA [1], where it is clearly said that:

  In the cells of extant organisms, the vast majority of the proteins in the
  mitochondria (numbering approximately 1500 different types in mammals) are
  coded by nuclear DNA, but the genes for some, if not most, of them are
  thought to be of bacterial origin, having been transferred to the eukaryotic
  nucleus during evolution. (citing [2])

[1] https://en.wikipedia.org/wiki/Mitochondrial_DNA

[2] https://doi.org/10.1016%2Fj.cels.2016.01.013