Transitioning into side control can be done by first switching into a particular hold known as ushiro-kesa-gatame (後袈裟固) or reverse scarf hold, where the chest points to the side, and the opponent's arm is controlled similarly to kesa-gatame.
Kami shiho gatame (上四方固, "upper four quarter hold down"), and its variations kuzure kami shiho gatame (崩上四方固, "broken upper four quarter hold down"), are the most common pinning holds applied from the north–south position in combat sports using a gi[citation needed].
Kami shiho gatame is one of the seven mat holds, Osaekomi-waza, of Kodokan Judo.
Shiho gatame is also one of the 25 techniques of Danzan Ryu's constriction arts, Shimete, list.
Graphic from http://judoinfo.com/techdrw.htm A straight over throw naturally leads to kami shiho gatame.