79:9 A minor who has reached the age of education and who understands to Whom brachos are recited, if he knows how to pronounce the letters properly, he may be called for Maftir on Shabbos or yom tov. This excludes the special haftaros of Zachor, Parah, Shabbos Shuvah, and the seventh day of Pesach, when we read David’s song in II Samuel chapter 22. Similarly, on the first day of Shavuos when we read Ezekiel’s vision of G-d’s “chariot” as the haftarah, the custom is to call an adult who is a Torah scholar. Finally, on Shabbos Chazon, the custom is to call the rabbi of the congregation.
79:10 It was only instituted to read the haftarah with brachos after reading all the aliyos from the Torah with their brachos. If a defect is found in the Torah scroll on a regular Shabbos, even during the final aliyah, if there isn't another Torah available, the result is that they won't recite the concluding bracha after that last aliyah. In such a case, we do not recite the brachos for the haftarah; rather, we read it without brachos. The same is true on a day that has a special Maftir when a defect is found even in Maftir. If, on a regular Shabbos, seven aliyos with their brachos were successfully completed, then a defect was found while reading an additional aliyah or Maftir, it would appear that the haftarah should be read with its usual brachos. (See Mishnah Brurah 143:29 and Bi’ur Halacha 284:1 s.v. asur for further discussion of this halacha.)