drivers: usb_dc_mcux: processing endpoint callbacks in ISR context causes assertion

[ottojo]

Describe the bug
When using USB networking, the driver accesses networking functions which lock mutexes from ISR context. This leads to failed assertion mutexes cannot be used inside ISRs..

• ecm_status_cb is registered as USB status callback here (apparently called via ISR)

• ecm_status_cb calls ecm_status_interface here

• ecm_status_interface calls netusb_enable here

• netusb_enable calls net_if_up here

• net_if_up locks mutex here

• netusb_enable calls net_if_up here

To Reproduce
(Working on providing a minimal example...)

Expected behavior
Assertion should not fail, the interface should not be enabled from ISR context.

Impact
The network interface seems to work, but this makes it impossible to me to use __ASSERT, since the program can't run with CONFIG_ASSERT enabled.

Logs and console output
(WIP)

Environment (please complete the following information):

• OS: Ubuntu 20.04
• Toolchain: Zephyr SDK 0.13.1
• Zephyr: 70b0734 (reasonably recent main branch)
• Board: teensy41

[jfischer-no]

@ottojo There is no workaround, USB_DeviceNotificationTrigger needs to be offloaded to a thread/workqueue.

[danieldegrasse]

@ottojo I can reproduce the error on a RT1064 EVK building the "echo_server" sample with the following command:
west build -p always -b mimxrt1064_evk samples/net/sockets/echo_server -DOVERLAY_CONFIG=overlay-netusb.conf -DCONFIG_ETH_MCUX=n -DCONFIG_ASSERT=y. On my board, #42019 fixes the issue (per @jfischer-no's suggestion of offloading the ISR to a thread) can you verify that branch works for you?