[PATCH 5/5] soundwire: qcom: add sdw_master_device support

[Pierre-Louis Bossart]

>> Add new device as a child of the platform device, following the
>> following hierarchy:
>>
>> platform_device
>>      sdw_master_device
>>          sdw_slave0
> 
> Why can't we just remove the platform device layer here and add 
> sdw_master_device directly?
> 
> What is it stopping doing that?

The guidance from Greg was "no platform devices, unless you really are 
on a platform bus (i.e. Device tree.)". We never discussed changing the 
way the Device Tree parts are handled.

The main idea was to leave the parent (be it platform-device or PCI 
device) alone and not add new attributes or references to it.

The scheme here is similar to I2C/SPI, you have a platform device 
handled by the Device Tree baseline, and a driver create an 
i2c_adapter/spi_controller/sdw_master_device.