Hotline bling

[Greta]

Phone Ring
The definition of this term is actually completely black and white. [Drakes] words actually translate directly.
Hotline = Phone
Bling = Ring
One could state he is singing I know when that cell phone ring, that can only [mean one] thing. It just so happens that in this song he is referring to a booty call as is affirmed by the mention of late night when you need my love
The term itself does NOT mean booty call. Your hotline could bling any [time of the day] and it could be your boss or even your mother.