Ok, at end with help from Huawei Support (excelent) I got the link working.
I'm sharing how to setup it in case it could be helpful for someone.
The problem was the way of configuring the OLT, as the VLANS do not work in the same way that they do in an ethernet switch.
To add two vlans (10 and 20) to the port 0 of the first board, you should use this commands in OLT
MA5800(config)# service-port 2 vlan 10 eth 0/1/0 multi-service user-vlan 10 tag-transform translate
MA5800(config)# service-port 3 vlan 20 eth 0/1/0 multi-service user-vlan 20 tag-transform translate
In the switch part the trunk should be configured like this:
[Huawei]interface XGigabitEthernet0/0/1
[Huawei-XGigabitEthernet0/0/1] port link-type trunk
[Huawei-XGigabitEthernet0/0/1] port trunk allow-pass 10 20
Thank you all for your help!!