Phil Jackson Engaged To Jeanie Buss -- Will You Be My Assistant Coach ... For Life?

Former LA Lakers coach Phil Jackson has finally popped the question to his longtime girlfriend Jeanie Buss -- after 12 years of dating -- but the real question ... could this affect the Zen Master's possible coaching gig with the Brooklyn Nets?

Our Lakers source tells us the engagement went down on Christmas day, but Jeanie -- daughter of Lakers owner Jerry Buss -- didn't reveal the ring until moments ago.

She posted a pic of the huge rock on Twitter with the caption ... "Phil finally gave me that ring I wanted!"