John C. Reilly is one of the most versatile actors working today. He has appeared in outrageous comedies (“Step Brothers,” “Walk Hard”), dramas (“Magnolia,” “The Aviator”), and even a musical — he was nominated for an Oscar for “Chicago.” He has worked with Martin Scorsese, Renee Zellwegger, and Will Ferrell. And this week, he stars in “Cyrus” as a man who finds his romantic life complicated by the title character. Cyrus is the adult son (Jonah Hill) of the woman his character is dating (Marisa Tomei). He still lives with his mother and has no interest in sharing her. I spoke to Reilly about working with the Duplass brothers, independent filmmakers who work in a genre sometimes described as “mumblecore,” small, improvised, films about authentically awkward moments without the usual easy, predictable resolutions in studio productions.