Multiple I2C PORTs.

[djconcept]

Hello, I would like to understand the logic, on the board, I find 3 I2C ports:

I2C-0
I2C-1
I2C-10

When i make this: 

Code:

ls /dev/*i2c*

I receive this

Code:

/dev/i2c-1  /dev/i2c-20  /dev/i2c-21

what exactly is the link?

Thank you in advance for your support.

[admin]

that's 3 i2c bus interface by raspberry pi CM4.
i2c-0,1,2 just for our mark on PCB.

[admin]

if you want to use i2c device extend GPIOs or sensor. please use I2C-1 port. just green terminal on the PCB.
--------------------------------------------------------------------
i2c-0: IDSDA,IDSCL default have connected with CSI0 and DSI0 camera and displayer.
IDSCL: (BCM2711 GPIO 1) GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
ID_SDA: (BCM2711 GPIO 0) GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
--------------------------------------------------------------------
i2c-10:
SDA0: I2C Data pin (BCM2711 GPIO44): typically used for Camera and Display. Internal 1.8kΩ pull up to CM4_3.3V
SCL0: I2C clock pin (BCM2711 GPIO45): typically used for Camera and Display. Internal 1.8kΩ pull up to CM4_3.3V