M/P nomenclature for axial-chirality
The (+)/(-) notation refers only to the sign of the experimentally measured optical rotation. This notation alone does not tell you anything about which enantiomer you have.

The M/P notation refers to the spatial arrangement of atoms (see https://en.wikipedia.org/wiki/Atropisomer for an explanation).

What is the relationship between (+)/(-) and M/P? NONE.
You cannot say a priori if a certain compound for which you know the spatial arrangement of atoms will give you a positive or negative optical rotation.
Similarly, you cannot deduce the spatial arrangement of atoms from an optical rotation measurement.

There are methods to establish the relationship between the two descriptors, which means assigning the absolute configuration of a chiral molecule.

People have come up with rules to relate the two (e.g. binaphthyls, biphenyls), and these rules often work. More specifically, I am talking about the so-called Exciton Chirality method by Harada and Nakanishi (see DOI: 10.1021/ar50056a001).

The reasons why it works (often) or fails (sometimes) go probably beyond the scope of the question, but if you are interested I can maybe look for some paper explaining the problems.