ASoC: SOF: Intel: Baytrail: clarify mutual exclusion with Atom/SST driver

Some distros select all options blindly, which leads to confusion and
bug reports. Since SOF does not support Baytrail-CR for now, and
UCM/topology files are still being propagated to downstream distros,
make SOF on Baytrail an opt-in option that first require distros to
opt-out of existing defaults.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191101173045.27099-2-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/Kconfig

@@ -101,6 +101,9 @@ config SND_SST_ATOM_HIFI2_PLATFORM_ACPI
 	  If you have a Intel Baytrail or Cherrytrail platform with an I2S
 	  codec, then enable this option by saying Y or m. This is a
 	  recommended option
+	  This option is mutually exclusive with the SOF support on
+	  Baytrail/Cherrytrail. If you want to enable SOF on
+	  Baytrail/Cherrytrail, you need to deselect this option first.
 
 config SND_SOC_INTEL_SKYLAKE
 	tristate "All Skylake/SST Platforms"

sound/soc/sof/intel/Kconfig

@@ -62,10 +62,18 @@ if SND_SOC_SOF_INTEL_ACPI
 
 config SND_SOC_SOF_BAYTRAIL_SUPPORT
 	bool "SOF support for Baytrail, Braswell and Cherrytrail"
+	depends on SND_SST_ATOM_HIFI2_PLATFORM_ACPI=n
 	help
 	  This adds support for Sound Open Firmware for Intel(R) platforms
 	  using the Baytrail, Braswell or Cherrytrail processors.
-	  Say Y if you have such a device.
+	  This option is mutually exclusive with the Atom/SST and Baytrail
+	  legacy drivers. If you want to enable SOF on Baytrail/Cherrytrail,
+	  you need to deselect those options first.
+	  SOF does not support Baytrail-CR for now, so this option is not
+	  recommended for distros. At some point all legacy drivers will be
+	  deprecated but not before all userspace firmware/topology/UCM files
+	  are made available to downstream distros.
+	  Say Y if you want to enable SOF on Baytrail/Cherrytrail
 	  If unsure select "N".
 
 config SND_SOC_SOF_BAYTRAIL