enable bridge crashes Linux

So, I think I made some progress.

1. I enable the bridges in Barebox by setting the status and bridge-enable properties.
2. In the Linux devicetree overlay, I only set the status property, not the bridge-enable property.

The Barebox DT (the "0x1" syntax matters, it seems):

&fpga_bridge0 {
	status = "okay";
	bridge-enable = <0x1>;
};

The Linux DT overlay:

/dts-v1/;
/plugin/;

/ {
	fragment@0 {
		target = <&base_fpga_region>;

		__overlay__ {
			#address-cells = <0x1>;
			#size-cells = <0x1>;

			// The .rbf file must be placed in /lib/firmware
			firmware-name = "soc_firwmare.rbf";
			fpga-bridges = <&fpga_bridge0 &fpga_bridge1>;
		};
	};

	/* Enable the lightweight FPGA to HPS bridge (lwhps2fpga) */
	fragment@1 {
		target = <&fpga_bridge0>;

		__overlay__ {
			status = "okay";
			// Don't set bridge-enable!
			// bridge-enable = <1>;
		};
	};

	/* Enable the HPS to FPGA bridge (hps2fpga) */
	fragment@2 {
		target = <&fpga_bridge1>;

		__overlay__ {
			status = "okay";
			// Don't set bridge-enable!
			// bridge-enable = <1>;
		};
	};
};

Then, I when I check the status of the bridges, I get what I expect:

# for f in /proc/device-tree/soc/fpga?bridge*; do echo $(basename $f)":" $(cat $f/status); done
fpga-bridge@ff600000: disabled
fpga-bridge@ffc25080: disabled
fpga_bridge@ff400000: okay
fpga_bridge@ff500000: okay
#

I didn't try to communicate between the HPS and the FPGA yet, but it looks promising.