Add MediaTek MT6873 devapc driver

[Neal Liu]

On Tue, 2020-06-09 at 11:32 -0600, Rob Herring wrote:
> On Tue, Jun 09, 2020 at 06:24:19PM +0800, Neal Liu wrote:
> > These patch series introduce a MediaTek MT6873 devapc driver.
> > 
> > MT6873 bus frabric provides TrustZone security support and data
> > protection to prevent slaves from being accessed by unexpected
> > masters.
> > The security violations are logged and sent to the processor for
> > further analysis or countermeasures.
> > 
> > Any occurrence of security violation would raise an interrupt, and
> > it will be handled by devapc-mt6873 driver. The violation
> > information is printed in order to find the murderer.
> 
> There's also a proposed driver with similar functionality[1]. Come up 
> with a common solution.
> 
> Rob
> 
> [1] https://lore.kernel.org/linux-arm-kernel/20200128153806.7780-1-benjamin.gaignard@st.com/

Actually, Mediatek devapc HW do the similar things. But the real
"firewall" functionality is implemented in TrustZone instread of REE.
This devapc-mt6873 driver is mainly handled the violation.

Bus firewall framework seems not cover this parts.