Is there a convention for precedence of operators in an additive category?

Is there a convention for precedence of operators in an additive category?

The laws for an additive category are that there must be a zero object,
binary products, that every Hom-set is an abelian group, and that the
morphism addition distributes over composition.
My question is a question about convention. If someone writes an
expression $f + g \circ h$, how should I parse this? As $(f + g) \circ h$
or as $f + (g \circ h)$?
Obviously, conventions are conventions, so if the question comes up, which
would have been used by Grothendieck or MacLane. If there is no general
agreement, that works too.