The question is kind of contained in the title but let me add a few words.
If $f$ is a cusp form of weight $k$ for $SL(2, \mathbb{Z})$ then Scholl constructed a Grothendieck motive $M(f)$. In this case $k$ is an even natural number.
What happens for modular forms of half weight? Is there some motivic construction attached to them? I would be particularly interested in the case of the $\eta$ function.
Thanks for your help.