I have recently purchased a Portal router, with the intention of porting mainline OpenWrt to it.
The Portal has a rather strange architecture, in that it actually has 2 separate SoCs: a QCA9563 handling normal router functions and providing the web interface, and a QCA9531 (FCC docs show QCA4531, but I have taken mine apart, and it definitely says 9531 both on the chip itself and in the boot log - aparently these two are identical chips intended for different use cases) responsible for the DFS "Fastlane" function and cloud/app-based manageability. Both SoCs run separate instances of OpenWrt 15.05 Chaos Calmer, with a custom web interface on the 9563, "uath"-based (=vendor?) wireless drivers, and a custom daemon on each SoC (called "rwdagent" on the 9563 and "rwdmanager" on the 9531) seemingly managing communications between the two SoCs. So far, I have been able to gain root access and install LuCi on both SoCs, and disable rwdmanager's "phone home" features.
The 9563 is located on the router's main logic board, and the boot log indicates that this board self-identifies as an "AP152" reference design (which it's definitely not, it's clearly a custom board). The 9531 (4531 in FCC docs) is on an M.2 daughterboard, which self-identifies as an "AP143". The communications between the 2 boards appear to go over an Ethernet link wired to unused pins on the M.2 connector, even though the PCI-E lanes also appear to be connected.
Any ideas where to get started with bringing up a modern OpenWrt on this device? Are such dual-SoC setups even supported in any useful way?