I would like to re paint/stain my wood railings on a covered porch but i am not sure if prior owner painted or used a solid color wood stain. If i am not sure what was used before, is it ok to just paint over it if stained before and vise versa if it was painted and i want to stain?

i do not plan on removing the orginal coating and appears only 1 coat(original). It is starting to chip in some places that i have already cleaned up plus gets very mildewy each year due to plants have in front of house, plus it is North side facing and gets zero sun. thanks.