uio_pruss on linux-ti 4.4.12

Hi all,

I am building a distro for beaglebone based on openembedded, I am using
kernel from meta-ti, which I want to configure to support uio_pruss
driver. I am applying following patch to kernel [1]. With this,
when DT node for pruss is enabled, the driver loads correctly, only
displaying one message in kernel log:

pruss_uio 4a300000.pruss: pins are not configured from the driver

But when I configure pinctrl to set some pins in PRU mode and add this
configuration to PRU node [2] then I get following line in kernel log:

[ 9.364820] pruss_uio 4a300000.pruss: No children

The messages I'm getting come from the patch (namely this part [3]).
So AFAIU, if I don't set the pinctrl, it will complain and go to the
rest of initialzation, but if pinctrl is set, it will try to find child
nodes of pruss in DT and then fail if there are none. But I am unsure on
why does it work that way? Should there be some child nodes of pruss in
DT? I did not see anyone using PRU adding any children to it (except
for replicape overlay [4]).

Anyway, I would be glad if someone provided some clarity how am I
supposed to configure DT and uio_pruss driver properly for PRU to work.

[1] https://raw.githubusercontent.com/RobertCNelson/bb-kernel/am33x-v4.7/patches/pru_uio/0001-Making-the-uio-pruss-driver-work.patch
[2] https://raw.githubusercontent.com/adamolek/beaglebone/master/pru/hcsr04/HCSR04-PRU.dts
[3] http://pastebin.com/raw/7VxrtSzD
[4] https://github.com/beagleboard/bb.org-overlays/blob/90dcb13667d9bf3649ab9b34faf5dd5fcf099403/src/arm/BB-BONE-REPLICAP-00B3.dts