Trouble getting sc16is752 to work / Devices not in /dev

[t0mn]

Hi!

I'm having trouble getting a sc16is752 to run (i2c).

In dmesg I see:
$this->bbcode_second_pass_code('', '[ 10.017045] serial serial0: tty port ttySC0 registered
[ 10.034955] serial serial1: tty port ttySC1 registered')

But those 2 ports are not showing up in /dev/
When I run the exact same setup on a Raspbian Buster, all is fine.

The hardware is a Raspberry Pi 3 and a serial expansion board:
https://www.waveshare.com/wiki/Serial_Expansion_HAT
OS is an up to date Archlinuxarm, Kernel 4.19.102-1, ARMv7

config.txt:
$this->bbcode_second_pass_code('', 'dtoverlay=sc16is752-i2c (overlay provided by Arch Distro)')

Address is 0x48
i2cdetect -y 1:

$this->bbcode_second_pass_code('', ' 0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --')

lsmod:
$this->bbcode_second_pass_code('', 'i2c_bcm2708 16384 0
sc16is7xx 20480 0
i2c_dev 16384 0')

/etc/modules-load.d/raspberrypi.conf:
$this->bbcode_second_pass_code('', 'snd-bcm2835
i2c-dev
sc16is7xx
i2c-bcm2708')

Any advice on how I could troubleshoot this further?

Thanks!