Hi Pablo,

Found the cause for the Help problem.

On CentOS, /boot/overlays/README is missing. It contains the help for all the dtoverlay commands...

I got the file from its original distro, and I put it under /boot/overlays/README.rasp for the demo:

[pi@myrpi ~]$ dtoverlay -h i2c-gpio
* Help file not found
[pi@myrpi ~]$ sudo mv /boot/overlays/README.rasp /boot/overlays/README
[pi@myrpi ~]$ dtoverlay -h i2c-gpio
Name:   i2c-gpio

Info:   Adds support for software i2c controller on gpio pins

Usage: dtoverlay=i2c-gpio,<param>=<val>

Params: i2c_gpio_sda            GPIO used for I2C data (default "23")

        i2c_gpio_scl            GPIO used for I2C clock (default "24")

        i2c_gpio_delay_us       Clock delay in microseconds
                               (default "2" = ~100kHz)

[pi@myrpi ~]$

Unfortunatelly, the files under this folder seem to belong to no package...

[pi@myrpi ~]$ rpm -qf /boot/overlays/i2c-gpio.dtbo
file /boot/overlays/i2c-gpio.dtbo is not owned by any package
[pi@myrpi ~]$

So, I'm stuck there, for now ...