If I'm not mistaken, Masechet Megillah mentions a few haftarot, I think, mainly for Yom Tov. I don't recall much mentioned about the weekly Shabbat haftarot.
In most Chumashim, I noticed that there are frequently different haftarot for Sephardim and Ashkenazim. Sometimes, these differences include Polish, Italian, and some other minhagim.
Who organized which haftarot should be said each week as well as for "special" occasions (e.g. Shabbat Rosh Hodesh, the 4 parshiot, etc.) and when where these compiled?