The poetic devices in "Mother" are metaphor and repetition. The mother uses metaphor to compare her life to a staircase that has imperfections and takes effort to climb. The poem also uses repetition...
life ain't crystal staircase- life isn't that easy
its an extended metaphor comparing life to stairs that it self is endless. you shouldn't give up even if your life was bad
I think that the extended metaphor is the actual title, "Mother to Son", and it is this because in the poem life is compared to a crystal staircase.
it's a poem about a mother encouraging her son. she says life wasn't easy for her but she didn't give up and neither should her son.