Indeed, it seems like a smartphone with a "Hotspot" feature can act as a Wi-Fi router.
After doing some research, as far as I understand, the network I've been asking about works as follows :
(external IP address)
(internal IP address)
/ | \
(IP address) (IP address) (IP address)
Wireless Drive Computer Wireless Printer
[file server] [file client] [print server]
The important thing is that each device must have a server running for the Computer to be able to use it.
I found some useful Linux commands along the way :
netstat -rn gives you the internal IP address of the Smartphone under the "Gateway" column.
ifconfig gives you IP address of the Computer itself connected to the Smartphone, in the "wlan" section.
ip neighbour gives you IP addresses of the other devices connected to the Smartphone.
IP addresses can be used to gain access to a device's features from a client, using the syntax protocol://ip_address.
I hope this will help someone.