[QUESTION] Public availability of the MHI specification

Hi,

I am looking into the MHI bus subsystem (drivers/bus/mhi/) to better 
understand the protocol and the semantics behind the MMIO register 
layout defined in drivers/bus/mhi/common.h. My motivation is that I 
would like to use MHI to communicate with a PCIe device rather than 
reinventing a similar protocol from scratch.

The in-tree documentation (Documentation/mhi/) gives a good 
architectural overview, and several comments in the code refer to the 
MHI specification by section number (e.g. drivers/bus/mhi/ep/main.c:57 
mentions "section 4.3, Interrupt moderation") and by version (commit 
48f98496b1de mentions "MHI spec v1.2"). However, I could not find a 
pointer to the specification document itself.

Could you tell me:
1. Is the MHI specification publicly available? If so, where can it be 
downloaded (Qualcomm developer portal, elsewhere)?
2. Is MHI intended/suitable for use with non-Qualcomm devices, or would 
you recommend against going down that path?

Thanks in advance for any pointer.

Regards,
Ludovic Desroches