Add support for rtl8821cu WiFi Dongle (#1899)

* Add rtl8821cu driver

* buildroot ee56159464...666868435d (1):
  > Merge pull request #2 from s-ol/fix-usb_modeswitch-systemd

* Add rtl8821cu support to all boards

Signed-off-by: s-ol <s+removethis@s-ol.nu>
Co-authored-by: Stefan Agner <stefan@agner.ch>

buildroot-external/package/rtl8821cu/0001-allow-arm-i386-external-control.patch

@@ -0,0 +1,21 @@
+Makefile: expose platform variables
+
+Signed-off-by: s-ol <s+removethis@s-ol.nu>
+
+diff --git a/Makefile b/Makefile
+index 22bd0e0..72321a4 100755
+--- a/Makefile
++++ b/Makefile
+@@ -96,9 +96,9 @@
+ ###################### MP HW TX MODE FOR VHT #######################
+ CONFIG_MP_VHT_HW_TX_MODE = n
+ ###################### Platform Related #######################
+-CONFIG_PLATFORM_I386_PC = y
+-CONFIG_PLATFORM_ARM_RPI = n
+-CONFIG_PLATFORM_ARM64_RPI = n
++CONFIG_PLATFORM_I386_PC ?= n
++CONFIG_PLATFORM_ARM_RPI ?= n
++CONFIG_PLATFORM_ARM64_RPI ?= n
+ CONFIG_PLATFORM_ANDROID_X86 = n
+ CONFIG_PLATFORM_ANDROID_INTEL_X86 = n
+ CONFIG_PLATFORM_JB_X86 = n

buildroot-external/package/rtl8821cu/Config.in

@@ -0,0 +1,5 @@
+config BR2_PACKAGE_RTL8821CU
+	tristate "Realtek 8821cu USB WiFi"
+	depends on BR2_LINUX_KERNEL
+	---help---
+	  Driver for RTL8821CU USB WiFi adapters (no firmware needed).

buildroot-external/package/rtl8821cu/rtl8821cu.mk

@@ -0,0 +1,20 @@
+RTL8821CU_VERSION = 8c2226a74ae718439d56248bd2e44ccf717086d5
+RTL8821CU_SITE = $(call github,brektrou,rtl8821CU,$(RTL8821CU_VERSION))
+RTL8821CU_LICENSE = GPL-2.0
+RTL8821CU_LICENSE_FILES = LICENSE
+
+RTL8821CU_MODULE_MAKE_OPTS = \
+	CONFIG_RTL8821CU=m \
+	KVER=$(LINUX_VERSION_PROBED) \
+	KBASE=$(LINUX_DIR) \
+	CROSS_COMPILE=$(TARGET_CROSS)
+
+ifeq (arm, $(filter arm, $(KERNEL_ARCH)))
+RTL8821CU_MODULE_MAKE_OPTS += CONFIG_PLATFORM_ARM_RPI=y
+RTL8821CU_MODULE_MAKE_OPTS += CONFIG_PLATFORM_ARM64_RPI=y
+else
+RTL8821CU_MODULE_MAKE_OPTS += CONFIG_PLATFORM_I386_PC=y
+endif
+
+$(eval $(kernel-module))
+$(eval $(generic-package))