You can use any SoC as the starting point for an open source smartphone. I don't think this is appropriate, though, given the inability to break out high-bandwidth busses from the board, e.g. for a video display or LTE networking.

3g is plenty fast, for the next few years at least. The only advantage of LTE is latency, and there's only LTE when you're in the middle of a city and probably have wifi anyway.

Owning a phone that came out like 3 months before 4g got built into everything (from high-end to cheap stuff), I can say I've never missed it. I'd rather they spend money on improving 3g reception, which is pretty good but could still be a lot better.

> 3g is plenty fast, for the next few years at least. The only advantage of LTE is latency

???? LTE is orders of magnitude faster.

> and there's only LTE when you're in the middle of a city and probably have wifi anyway.

Not in the US. Every marginally populated area has it.

> LTE is orders of magnitude faster.

Yeah but that doesn't make 3g slow. Like I said, 3g is plenty fast, meaning it's fast enough for mobile browsing and even watching videos (though videos over mobile data is just stealing money out of your own wallet, but that's a separate issue). That 4g/LTE is faster doesn't make 3g any slower. The only slightly noticeable advantage of LTE is latency or downloading large files (which you wouldn't do over a metered connection if you had a choice).

> Not in the US. Every marginally populated area has it.

Looking at coverage maps of the Netherlands, I guess I'm outdated. There's little difference between 3g and 4g anymore. I remember not long ago when 3g was nearly everywhere (so close to 100% coverage) and then they started putting down 4g everywhere. 3g advancement stopped altogether. Right now it looks like they just upgraded the 3g spots to 3g+4g and forgot about advancing the network at all.

In theory, yes, but the lack of LVDS/MIPI display connector/driver (or even HDMI) makes it difficult to connect any practical display on it.

What are the LCD-Dx lines for?

No idea. I'm not familiar with the CHIP Pro, just quickly read the datasheet. The SOC contains Mali400 GPU, so in theory it should capable for video output, but I can't find any mentioning whether the video capability is enabled in hardware/software level in CHIP Pro (i.e pins wired & Linux driver).

Raspberry Pi has similar problem: although it uses a SOC designed for mobile applications, there are no open source solutions to connect generic smartphone displays to DSI port, and HDMI is very bulky/over-engineered solution for transferring video signal over few centimeters. (Blame Broadcom, not the Foundation.)