Merge #19538 #19547

19538: drivers/mtd_default: add external declarations for mtd* r=benpicco a=gschorcht

### Contribution description

The `mtd_default` module defines `MTD_NUMOF`, if not present, based on the `MTD_*` defines. These defines are set to the corresponding `mtd*` MTD device pointer variables in the board definitions. However, not all `mtd*` MTD device pointer variables are  always made known by external variable declarations. An example are SD Card Interfaces that are defined via the `mtd_sdcard_default` module. As a result, it may be necessary for an application using `mtd_default` to declare an external MTD device pointer variable `mtd`. To be able to use SD card for testing MTD based application, `mtd_default` also declares up to six `mtd*` MTD device pointer variables.

### Testing procedure

Use any board without SD Card definition and compile `tests/pkg_litllefs`,  `tests/pkg_litllefs2` or `tests/pkg_spiffs`, for example to use a temporary connected SD Card interface.
```
CFLAGS='-DMTD_0=mtd0 -DCONFIG_USE_HARDWARE_MTD' USEMODULE='sdcard_spi mtd_sdcard_default' BOARD=nucleo-f411re make -j8 -C tests/pkg_littlefs
```
Without this PR, compilation fails due to undeclared `mtd0` variable
```
tests/pkg_littlefs/bin/nucleo-f411re/riotbuild/riotbuild.h:2:15: error: 'mtd0' undeclared (first use in this function)
    2 | #define MTD_0 mtd0
      |               ^~~~
```
Compilation works with this PR and the temporary connected SD Card interface can be used with this test applications.

### Issues/PRs references


19547: pkg/openthread: set event callback before netdev init r=benpicco a=bergzand

### Contribution description

When using openthread with the ieee802154_submac module, a hard fault is triggered otherwise because the submac's init function calls the event_handler callback.


### Testing procedure

Flash the `examples/openthread` application on the nrf52840dk board. Without this patch the board is stuck in a hard fault loop. With this patch the application starts successfully.


### Issues/PRs references

None


Co-authored-by: Gunar Schorcht <gunar@schorcht.net>
Co-authored-by: Koen Zandberg <koen@bergzand.net>

drivers/include/mtd_default.h

@@ -57,6 +57,31 @@ extern "C" {
 
 #endif /*  !defined(MTD_NUMOF) && !DOXYGEN */
 
+#if !DOXYGEN
+
+/**
+ * @brief   Declare `mtd*` according to the number of MTD devices
+ */
+#if MTD_NUMOF > 0
+extern mtd_dev_t *mtd0;
+#endif
+#if MTD_NUMOF > 1
+extern mtd_dev_t *mtd1;
+#endif
+#if MTD_NUMOF > 2
+extern mtd_dev_t *mtd2;
+#endif
+#if MTD_NUMOF > 3
+extern mtd_dev_t *mtd3;
+#endif
+#if MTD_NUMOF > 4
+extern mtd_dev_t *mtd4;
+#endif
+#if MTD_NUMOF > 5
+extern mtd_dev_t *mtd5;
+#endif
+#endif /* !DOXYGEN */
+
 #if defined(MODULE_MTD_SDCARD_DEFAULT)
 extern mtd_sdcard_t mtd_sdcard_dev0;
 #endif

pkg/openthread/contrib/netdev/openthread_netdev.c

@@ -84,8 +84,8 @@ static void *_openthread_event_loop(void *arg)
 
     event_queue_init(&ev_queue);
 
-    netdev->driver->init(netdev);
     netdev->event_callback = _event_cb;
+    netdev->driver->init(netdev);
 
     netopt_enable_t enable = NETOPT_ENABLE;
     netdev->driver->set(netdev, NETOPT_TX_END_IRQ, &enable, sizeof(enable));