Is there a preferred placement of termination resistor for a differential clock line?

Termination resistors sit at one of two places: As close to the driver as possible (for source termination), or as close to the end of the trace as possible (for the kind of termination that you have).

Notice that I said "as close to the end of the trace as possible", and not "as close to the receiver as possible"? There is a difference!

Most people think of the signal chain for end termination being like this: Driver --> Long Trace --> Termination --> Receiver. But that is incorrect. The termination should be at the end of the signal. Like this: Driver --> Long Trace --> Receiver --> Termination.

If you have several receivers, then you get this: Driver --> trace --> receiver1 --> trace -> receiver2 --> termination.

The reason for this is that the termination prevents the signal from reflecting back to the receiver(s) and corrupting their signal. In theory you could have a super long trace from the last receiver to the terminator and that would work just fine!

That is why your termination resistor is not near the driver-- because it doesn't have to be. The resistor is at the end of the line, right where it should be. There are other reasons why the resistor is placed that far away, but that isn't too important.

As for the little squiggles, that is because in a differental signal the lengths of the two traces should be identical in length. The Squiggles are done to adjust the length of one trace to make it match the other trace.

Like embedded.kyle says, the squiggle is a clue, but I disagree about the meaning. It's absolutely certain that they need to design with controlled impedance for 300 MHz, squiggle or now squiggle.

What the squiggle says to me is that they are being very careful about matching the trace length between the two lines in the differential pair. The reason to do this is to minimize common-mode reflections on the line, which could conceivably cause an emi problem. I think they moved the terminating resistor to make room for the squiggle.

However, given the frequency (300 MHz) and the size of the squiggle, I believe they are over-designing this. That small a squiggle is unlikely to have any meaningful effect at that frequency.

That said, they don't cause any problems with this design. What they've done is just move the termination down the line past the receiving part. This is a perfectly good design, and better than what you usually see, which is to put the termination first and then run a stub for a few more mm to reach the receiving part. In the case you show, the receiving part just causes a slight capacitive shunt at a midpoint on the line.