DTO:
/*
* pru dts file BB-BONE-PRU-00A0.dts
*/
/dts-v1/;
/plugin/;

/ {
  compatible = "ti,beaglebone", "ti,beaglebone-black";

  /* identification */
  part-number = "BB-BONE-PRU";
  version = "00A0";

  exclusive-use =
    "P8.12";

  fragment@0 {
    target = <&am33xx_pinmux>;
    __overlay__ {
      mygpio: pinmux_mygpio{
        pinctrl-single,pins = <
          0x30 0x06
          >;
      };
    };
  };

  fragment@1 {
    target = <&ocp>;
    __overlay__ {
      test_helper: helper {
        compatible = "bone-pinmux-helper";
        pinctrl-names = "default";
        pinctrl-0 = <&mygpio>;
        status = "okay";
      };
    };
  };

  fragment@2{
  target = <&pruss>;
    __overlay__ {
      status = "okay";
    };
  };
};


=========================
Load DTO:
sudo sh -c "echo cape-bone-pru > /sys/devices/bone_capemgr.9/slots"

=========================
Also enable PRU (?):
# echo BB-BONE-PRU-01 > /sys/devices/bone_capemgr.*/slots

==========================
See if Switch attached to P8.12 is pressed:
TODO:
        QBBC TODO, r31.t14
        MOV  R31.b0, PRU0_ARM_INTERRUPT+16
        HALT


=========================
RESULT: the interrupt is never fired (note, if the qbbc is removed, the interrupt does work)