Just before someone like
@Maxperson only reads the initial bolded section
"ARCHFIENDS AND CLERICS
The demon lords and archdevils described in this chapter cannot grant spells to clerics. Instead, they act as patrons for clerics who devote themselves to abstract sources of divine power, and they assist the clerics of evil gods. They have worshipers who perform sacrifices in their name, but they don’t run organized religions the way gods do.
If you want the demon lords and archdevils to have organized faiths and grant spells, it’s easy to do so. Chapter 6 identifies which domains each archfiend would be associated with (see the Cleric Domains section in the spell lists). If you have the Deities and Demigods book, you can give each demon lord and archdevil divine rank 1 and adjust their statistics accordingly."
So, the book said yes and no at the same time.