  Intrinsic topological superconductors have protected gapless Majorana modes,
bound and/or propagating, at the natural boundaries of the sample, without
requiring field, defect, or heterostructure. We establish the complete
classification/construction of intrinsic topological superconductors jointly
protected by point-group and time-reversal symmetries in three dimensions. This
is obtained from enumerating distinct ways for stacking $n$th-order irreducible
building blocks, minimal anomalous surface states of $n$th-order topological
superconductors. Particularly, our method provides a unified description of
possible surface anomalies away from high-symmetry points/lines in terms of the
homotopy group of the surface mass field.
