Add an alexa/google assistant device to HomeAssistant

Hi,
I have a smart thermostat that can be controlled by alexa and also google assistant.
I want add it to home assistant but the device not has public api or something available to integrate it with home assistant.
Do you know if there is a way to add an alexa/google enabled device to hass??

Thank you

Nobody can answer me??
Pleaseā€¦

I develop a custom component for the thermostat.