Take a name starting with Mc, like McDonald. How do you hyphenate it? McDon-ald or Mc-Don-ald?
If possible avoid hyphenating a surname at all, that is tolerate more spacing in the line than you would generally.
This is particularly so if the name is first introduced with this piece and not repeated shortly afterwards. Since you are introducing the name you'd want to be clear that this was a hyphenation due to the end of the line, rather than a peculiarity of the person's names. (Consider, after all, that people can have all manner of peculiarities about names, so you can't be sure there isn't someone out there that spells their name Mc-Donald all the time).
But if you have to hyphenate a potential hyphenation point comes after the Mc and then the rest according to whatever rules you generally use (likely Don and ald). If you prefer to favour breaking at the join within a closed-compound word (I do) then you should favour the break after Mc as these names are compounds in origin.
Hence in order of preference:
McDonald [just went onto the next line and avoided hyphenation entirely]