Arnold's Kid Joseph Baena -- I've Been Validated ... By the DMV

Arnold Schwarzenegger's son Joseph Baena is moppin' up the highway now ... because he just got his driver's license!

16-year old Joseph Baena and mom, Mildred, rolled up to the DMV in Bakersfield yesterday in the brand spankin' new Jeep Rubicon Arnold gave him for XMAS.

Joseph passed muster and drove out a full-fledged driver.

On the ride home ... mom rode shotgun.