@mo123 Thanks, the work was more involved than that because I had to define some new dts nodes and a new GPIO interrupt for the headphone hotplug detection. The pinctrl definitions for the i2s bus were good upstream and didn’t require modification.
So now I have a patch and working analog audio in the upstream kernel 
However I am very very sad because the audio connector broke on my v1.3 rock-pi-4 just like described here. so I can’t really enjoy the fruit of my effort 
Anyway I’ll send a patch to the upstream kernel and LibreELEC to get it working for everyone.