  Owing to ever increasing gate fidelities and to a potential transferability
to industrial CMOS technology, silicon spin qubits have become a compelling
option in the strive for quantum computation. In a scalable architecture, each
spin qubit will have to be finely tuned and its operating conditions accurately
determined. In this prospect, spectroscopic tools compatible with a scalable
device layout are of primary importance. Here we report a two-tone spectroscopy
technique providing access to the spin-dependent energy-level spectrum of a
hole double quantum dot defined in a split-gate silicon device. A first
GHz-frequency tone drives electric-dipole spin resonance enabled by the
valence-band spin-orbit coupling. A second lower-frequency tone (approximately
500 MHz) allows for dispersive readout via rf-gate reflectometry. We compare
the measured dispersive response to the linear response calculated in an
extended Jaynes-Cummings model and we obtain characteristic parameters such as
g-factors and tunnel/spin-orbit couplings for both even and odd occupation.
