[petsc-users] Nested field split

I've seen threads in the archives about nested field split but I'm not sure they match what I'm asking about. I'm doing a Schur field split for a porous version of incompressible Navier-Stokes. In addition to pressure and velocity fields, we have fluid and solid temperature fields. I plan to put all primal variables in one split and the pressure obviously in the Schur split. Now within the "primal variable split" a user is wondering whether we can do a further split, e.g. perhaps an additive split with the solid temperature split out from the velocities and fluid temperature (the former is almost pure conduction whereas the latter may be advection dominated). Is this possible? Alex