  We give an overview of various determinations of $\gamma/\phi_3$ with the
help of $B_s$ decays into charmed final states, distinguishing between
transitions with tree and penguin contributions and pure tree decays. In the
corresponding strategies, the $U$-spin flavour symmetry of strong interactions
provides a very useful tool, and offers interesting "by-producs" for the
$B$-physics programme at the LHC, including the control of the penguin
uncertainties in the determinations of the $B^0_d$-$\bar B^0_d$ and
$B^0_s$--$\bar B^0_s$ mixing phases $\phi_d$ and $\phi_s$ from $B_d\to J/\psi
K_S$ and $B_s\to J/\psi\phi$, respectively, and an alternative extraction of
the latter phase through $B_s\to D_s^+D_s^-$. Finally, we point out that the
cleanest determinations of the mixing phases $\phi_s$ and $\phi_d$ are offered
by the pure tree decays $B_s\to D_\pm K_{S(L)}$ and $B_d\to D_\pm\pi^0,
D_\pm\rho^0, ...$, respectively, which are very interesting for the searches of
new physics.
