DevOps and ITIL are both ITSM
DevOps and ITIL are both ITSM. The patterns are the same though the execution is different.
I enjoy explaining to DevOps folk that service management is not one theory among many. Service management models reality and ITSM is the description of IT reality: of all the activities that happen in the real world. Everybody manages change; everybody releases into the world; everybody manages capacity and availability and continuity; everybody manages incidents and requests ; everybody strategises, plans, designs, and builds services; everybody does improvement. The levels of maturity might very but these practices are present in every organisation.
DevOps is one codification of that reality and ITIL is another. They see the world through different lenses.
A nice analogy came from @cshl1 on Twitter: orchestras and jazz bands. ITIL encourages a high level of formality whereas DevOps encourages improvisation and fluidity. Same tone scale, same instruments. It's all music.
Or to take another analogy: different paths up the same mountain.
ITIL and DevOps are compatible because they describe the same world (Gene Kim and others have argued that well). Both have to bend a little in the real world, and they meet in practical reality. Any "horse" organisation with legacy and innovation will need both.