  We discuss the expected X-ray spectral and variability properties of black
hole accretion discs at high luminosity, under the hypothesis that radiation
pressure dominated discs are subject to violent clumping instabilities and, as
a result, have a highly inhomogeneous two-phase structure. After deriving the
full accretion disc solutions explicitly in terms of the parameters of the
model, we study their radiative properties both with a simple two-zones model,
treatable analytically, and with radiative transfer simulations which account
simultaneously for energy balance and Comptonisation in the hot phase, together
with reflection, reprocessing, ionization and thermal balance in the cold
phase. We show that, if not only the density, but also the heating rate within
these flows is inhomogeneous, then complex reflection-dominated spectra can be
obtained for a high enough covering fraction of the cold phase. In general,
large reflection components in the observed X-ray spectra should be associated
with strong soft excesses, resulting from the combined emission of ionized
atomic emission lines. The variability properties of such systems are such
that, even when contributing to a large fraction of the hard X-ray spectrum,
the reflection component is less variable than the power-law like emission
originating from the hot Comptonising phase, in agreement with what is observed
in many Narrow Line Seyfert 1 galaxies and bright Seyfert 1. Our model falls
within the family of those trying to explain the complex X-ray spectra of
bright AGN with ionized reflection, but presents an alternative, specific,
physically motivated, geometrical setup for the complex multi-phase structure
of the inner regions of near-Eddington accretion flows.
