Why ADC helper driver does not work?

In my project I use ADC. But I try to avoid dynamic overlay loading in order to increase boot speed. 
So I move code from ADC overlay (BB-ADC-00A0.dts) to main device tree source (am335x-boneblack.dts):

 / {

        ocp {
                /* ADC filesystem helper
                test_helper: helper {
                        compatible = "bone-iio-helper";
                        vsense-name  = "AIN0", "AIN1", "AIN2", "AIN3", "AIN4", "AIN5", "AIN6", "AIN7";
                        vsense-scale = <100     100     100     100     100     100     100     100>;
                        status = "okay";

/* Enable ADC */
&tscadc {
        status = "okay";

        adc {
                ti,adc-channels = <0 1 2 3 4 5 6 7>;

After boot I found out that directory /sys/devices/ocp.*/helper.*/ does not contain AIN files. dmesg out dos not contain messages from 
bone-iio-helper driver. Somehow bone-iio-helper driver haven't been loaded while device tree processing. 

Is there a way to fix this issue?

Which OS?
uname -a
cat /etc/dogtag
cat /etc/debian_version ###if debian

If the device tree was loaded and you have a late version of debian,
probably you need to look in /sys/devices/platform/ocp/ for the
directory 44e0d000.tscadc
There you will find the directories TI-am335x-adc/iio\:device0
Inside, you will find in_voltage[06].raw
These correspond to the AIN[0-6] for earlier OSes.

If the device tree was not loaded check dmesg.