Unexpected device ordering from FDT node sorting

[Sergii Rudchenko <sergii%rudchenko.nl@localhost>]

Hi NetBSD folks,

Following up on my discussion with Chris (bad@) at EuroBSDCon '26.

While tinkering with NetBSD on RPi Zero I have found that the order of 
i2c buses is different from Linux and OpenBSD because NetBSD is sorting 
FDT nodes by phandle (see fdt_get_order in sys/dev/fdt/fdtbus.c).

In the BCM2835 datasheet:
    There are three BSC masters inside BCM. The register addresses 
starts from
    * BSC0: 0x7E20_5000
    * BSC1: 0x7E80_4000
    * BSC2 : 0x7E80_5000

In the DTB:
    $ grep i2c@ bcm2835-rpi-zero-w.dts
                    i2c@7e205000 {
                    i2c@7e804000 {
                    i2c@7e805000 {
                    i2c0 = "/soc/i2c@7e205000";
                    i2c1 = "/soc/i2c@7e804000";
                    i2c2 = "/soc/i2c@7e805000";

A basic debug log in `bsciic_fdt_attach` shows the following:
    [     1.000000] bsciic0: SERGII Attaching a BSC at <0x7e805000 0x1000>
    [     1.000000] bsciic1: SERGII Attaching a BSC at <0x7e205000 0x200>
    [     1.000000] bsciic2: SERGII Attaching a BSC at <0x7e804000 0x1000>

It guess it is just a cheap way to avoid topological sorting of FDT 
nodes, but the resulting order of devices is confusing.

I realize that _changing_ this behavior is also tricky because upon 
NetBSD upgrade it will suddenly change the device order for everyone who 
relies on the current behavior. Yet, Chris has persuaded me to share my 
findings, so here I am :)


Best regards,
Sergii