meta-zephyr-core/bsp: Restructure into sublayers

This commit restructures meta-zephyr into meta-zephyr-core and
meta-zephyr-bsp. It moves machine definitions into meta-zephyr-bsp
in preparation for adding the autogenerated zephyr machines.

Signed-off-by: Eilís Ní Fhlannagáin <elizabeth.flanagan@huawei.com>
Signed-off-by: Naveen Saini <naveen.kumar.saini@intel.com>

meta-zephyr-core/classes/zephyr-flash-bossac.bbclass

@@ -0,0 +1,50 @@
+#@DESCRIPTION: class file to flash boards like Arduino Nano BLE which depends on bossac for flashing
+
+python do_flash_usb() {
+    import shutil
+    import subprocess
+    import serial.tools.list_ports
+
+    # Note: make sure the installed bossac is set to PATH before running flash_usb()
+    # Check if bossac is avaiable for flashing
+    origbbenv = d.getVar("BB_ORIGENV", False)
+    bossac_path = shutil.which("bossac", path=origbbenv.getVar('PATH'))
+
+    if not bossac_path:
+       bb.fatal("ERROR: bossac not found, please install first and add to PATH")
+
+    board = d.getVar('BOARD')
+
+    if board == 'arduino_nano_33_ble':
+        # find the serial port to which board is connected to
+        for port in serial.tools.list_ports.comports():
+            if 'Arduino Nano 33 BLE' in port.description:
+                serial_port = port.device
+                break
+        else:
+            bb.fatal("ERROR: board not connected for flashing. Connect via USB and enable permission to connected port")
+
+        image = "%s/%s.bin" % (d.getVar('DEPLOY_DIR_IMAGE'), d.getVar('PN'))
+
+        command = [bossac_path, '-p', serial_port , '-R', '-e', '-w', '-v', '-b', image]
+    else:
+        bb.fatal("ERROR: Unsupported board %s" % board)
+
+    bb.note("command: %s" % command)
+    bb.plain("Attempting to flash board: %s" % board)
+
+    # Random failure are a possibility here, retry till there is a success for finite times
+    for _ in range(10, 0, -1):
+        try:
+            subprocess.check_call(command)
+            bb.plain("Bossac Flashing board: %s Success " % board)
+            break
+        except subprocess.CalledProcessError as e:
+            bb.warn("Failed to flash %s (error code: %s). Retrying after 1 second..." % (board, e.returncode))
+            time.sleep(1)
+}
+
+addtask do_flash_usb after do_deploy
+
+do_flash_usb[nostamp] = "1"
+do_flash_usb[vardepsexclude] = "BB_ORIGENV"