Johnson is .307/.361/.452 and can play all three outfield positions, and hits left-handed pitching especially well, .313/.370/.469 for his career.
Maholm is pitching to a 3.74 ERA in just over 120 innings for the Cubs this year.
The Cubs will get RHP Jacob Brigham in the trade for Soto. Brigham has 4.28 ERA in 124 innings this season at Double-A Frisco. The corresponding move led to the Rangers designating catcher Yorvit Torrealba for assignment.