Student or Learner
when we say:
"I'll give you a shout."
Do we mean merely that I'll notify you or we specifically mean I'll notify you BY shouting or crying out loud?
It may have originated with a notification by actually shouting or hollering for someone. I can imagine people shouting across the yard for their neighbors or hollering at the gate to let them know there's some important news. However, when we say it today, it doesn't have to imply actual shouting, just the notification. We might also say, "I'll give you a call."
Shout is a metaphor for call, and means on the phone, or by extension, other digital media.
"I'll give you a shout" means that I will contact you (by phone, by email, whatever). "I'll give you a shout-out" means that I will acknowledge you publicly (for example, if I'm accepting an award, I might say "I'd like to give a shout-out to my drama teacher, Mr. Thompson, who encourage me to become an actor."
Yes, that's a case where he might actually shout to notify the passenger.