B737 Captain reported encountering wake turbulence on descent into PHX in trail of a B737-800.

Narrative

I was the Pilot Flying while descending on the EAGUL 6 Runway 8 transition into PHX. Autopilot was engaged in LNAV/VNAV and speed window was open set to 210 KIAS. We were following a -800 aircraft about five miles in front of us. Prior to HOMRR; ATC slowed both of us to 210 KIAS which put us both high on the profile. We both notified ATC that we would be high for HOMRR at that speed; which ATC acknowledged. Just prior to BOHTX around 13;500 feet MSL; we encountered light turbulence and the aircraft rolled left to about 18-20 degrees. I grasped the control and the autopilot disconnected. I rolled the aircraft back and may have over corrected and it rolled about 5 degrees back to the right and felt like it was wallowing around a bit in response to the wake. As I corrected the pitch back to the flight director; I noticed we were below the 13;000 feet restriction. I was not sure if we had just passed or were still over BOHTX; so we may have busted the 13;000 feet restriction. I think I saw 12;700 feet. I engaged the autopilot back into LNAV/VNAV and we continued without further events. The First Officer reported light turbulence over the fix. That is when I asked ATC what we were following and reported the wake encounter. He replied with -800 was the preceding aircraft.